(CNN) -- The surviving suspect in the Boston bombings has told investigators he and his brother planned to bomb Times Square, New York City Mayor Michael Bloomberg said Thursday.
"Last night we were informed by the FBI that the surviving attacker revealed that New York City was next on their list of targets," Bloomberg said.
The two came up with the plan spontaneously after the Boston bombing, as they talked in an SUV they hijacked, New York City Police Commissioner Ray Kelly said.
Dzhokhar Tsarnaev initially told investigators that he and his brother, Tamerlan Tsarnaev, had talked about going to New York to "party." Then in a second round of questioning Sunday evening into Monday morning -- during which Kelly said the suspect was "a lot more lucid" than the first time he was interviewed -- he revealed they planned to use their remaining explosives there, Kelly announced.
The plan "fell apart" when the SUV ran low on fuel in the Boston area and the Tsarnaevs ordered the driver to pull into a gas station, Kelly said. The driver escaped during the refueling, he said, and police subsequently caught up with the Tsarnaevs.
The brothers had five pipe bombs and a "pressure-cooker bomb" -- the latter similar to the bombs used in the Boston blasts -- with them in the SUV, Kelly said.
There is no evidence that New York City is currently a target of a terror attack stemming from the Boston bombings, Kelly added. Still, he said that authorities are investigating two visits that the surviving suspect made to New York City last year.
In one of those trips, in April 2012, Dzhokhar Tsarnaev is photographed in New York's Times Square.
One person pictured with him in Times Square remained in federal custody Thursday, as he's been for the last six days, on alleged visa violations.
This man, whom a federal law enforcement source said Dzhokhar shared a cell phone with, was originally detained last Friday with another person when federal agents swarmed a residence thinking Dzhokhar might be inside, a federal law enforcement source said.
Neither of these two detained men -- both foreign exchange students from Kazakhstan at the University of Massachusetts-Dartmouth, where Dzhokhar also was enrolled -- have been linked to the Boston Marathon attack. Yet investigators hope they can better piece together the suspected bombers' movements before and after the marathon.
"These guys are not being cut loose immediately, and there's a reason why," the federal law enforcement source said.
Sources: No gun found in boat
Dzhokhar Tsarnaev apparently was unarmed when he was wounded in a barrage of gunfire that ended with his capture after a tense standoff, sources told CNN Thursday.
No firearm was found in the boat where he was hiding, in the yard of a home in the Boston suburb of Watertown, Massachusetts, said several sources familiar with the investigation, from different agencies.
Earlier, Tsarnaev and his older brother, Tamerlan Tsarnaev, had allegedly shot and killed a Massachusetts Institute of Technology campus police officer sitting in a patrol car. Shortly afterward, the two engaged in a shootout with police. Tamerlan, 26, died after the shootout.
It's unclear why Dzhokhar, 19, may have hidden without any weapons.
Authorities have previously said in a criminal complaint that there was a standoff involving gunfire before Dzhokhar's capture.
Watertown Police Chief Edward Deveau told CNN's Wolf Blitzer on Saturday that it was his understanding that the suspect fired from the boat.
Dzhokhar Tsarnaev remains in fair condition at a Boston hospital, where he has communicated with authorities.
Authorities in the Russian republic of Dagestan interviewed the suspects' parents in the search for clues and insight into what may have led the brothers to turn the Boston Marathon finish line into a gruesome scene of terror.
Suspects' father plans to go to U.S.; mother insists bombing fake
The suspects' mother, speaking to CNN's Nick Paton Walsh, didn't want to accept the reality of the bombing, saying it was fake.
"That's what I want to know, because everybody's talking about it -- that this is a show, that's what I want to know. That's what I want to understand," said Zubeidat Tsarnaev.
She has seen a video pushing the wild idea, she said, adding that there was no blood -- and that paint was used instead.
But her disbelief broke down when she spoke of the victims.
"I really feel sorry for all of them. Really feel sorry for all of them," she said, her voice cracking. But she remained resolute that her sons, Dzhokhar, 19, and Tamerlan, 26 were not involved.
Later Thursday, after talking to the press, Zubeidat Tsarnaev said she'd called an ambulance to take her husband, who has a history of medical problems, to a hospital in the southern Russian city of Makhachkala. It was not immediately known if Anzor Tsarnaev was ever admitted to a hospital and, if so, if he is still there.
Anzor Tsarnaev had told reporters that he plans to go from Dagestan to the United States in the coming days.
His wife is not planning to join him.
She's wanted on 2012 felony charges of shoplifting and property damage in Massachusetts, according to court officials.
The family lived there before she jumped bail; the parents moved the same year to Dagestan, a semiautonomous region of Russia, officials said.
Tamerlan Tsarnaev's body remains unclaimed. Relatives in the United States have publicly said they are ashamed of the two young men. Several Boston-area imams have said they would feel uncomfortable presiding over Tamerlan's funeral.
Detonated by remote
The brothers used a remote control device similar to those used to guide toy cars to detonate the two bombs in Boston, said Rep. Dutch Ruppersberger, a Maryland Democrat and member of the House Select Committee on Intelligence.
A law enforcement official told CNN Thursday that at least one of the two bombs -- the second to explode -- was detonated by remote control.
While video taken near the scene of the explosions shows Dzhokhar Tsarnaev talking on a cell phone, it is not known whether he used it to trigger a device, a law enforcement official said.
Tsarnaev has indicated that his older brother planned the attack and described him and his brother as self-radicalized jihadists, according to a U.S. government source.
He has denied any direct influence from terror organizations such as al Qaeda.
The teenager cited the U.S. wars in Afghanistan and Iraq as motivating factors behind the attack, a U.S. government official said.
He has been charged with using and conspiring to use a weapon of mass destruction resulting in death and one count of malicious destruction of property by means of an explosive device resulting in death.
Of the more than 260 people who were hurt in the marathon bombings, 33 were still hospitalized Wednesday night, according to a CNN tally. One person was in critical condition at Boston Medical Center.
According to a source familiar with the investigation, authorities are looking into the possibility that Tamerlan Tsarnaev helped finance the bomb plot through drug sales.
Putin: 'We were right'
Russian President Vladimir Putin on Thursday urged closer cooperation between other countries' security services after the Boston Marathon bombings.
"If we combine our efforts, we will not suffer blows like that," he said during a live televised call-in session in Moscow on Thursday.
The Tsarnaevs are originally from the embattled Russian republic of Chechnya but fled from the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan and moved at different times to the United States.
In his first on-camera comments since the bombing, Putin also lashed out against those in the West who have slammed Russia for human rights abuses in its actions toward Chechnya.
"Russia is a victim of international terrorism itself. Russia is among the first victims, and I hate it when our Western partners call our terrorists -- who committed some heinous crimes in Russia -- when they call them freedom fighters and never call them terrorists. They supported them. They provided media support for them, financial support for them, political support -- sometimes directly, sometimes indirectly. But they always supported their actions in Russia.
"And we always told our partners, instead of general declarations you should have closer cooperation between our security services. And now these two criminals confirmed that we were right. "
He added, "Of course, we can speculate forever on the tragedy of the Chechen people when they were deported by the Stalin regime. But the Chechens were not the only victims."
Lawmaker: Obama administration gets 'ultimate blame'
Dagestan has become a focus for investigators, especially given that Tamerlan Tsarnaev went there during a six-month trip to Russia last year.
Officials have been looking into what he may have done there. The young man is believed to have posted videos online tied to militant jihadists in the region.
On two occasions before that -- in March and late September 2011 -- Russian authorities asked U.S authorities to investigate Tamerlan Tsarnaev.
Zubeidat Tsarnaev said the FBI had visited her family "several times" in 2011 with questions about Tamerlan's "Islamic interests."
A senior U.S. official with direct knowledge of information from the Russians said that the case then "was extremely thin," adding that Russia wanted Tamerlan Tsarnaev questioned to see if he and others had become "radicalized."
Lawmakers are asking whether the FBI and CIA failed to share information.
Sources told CNN that Russia had separately asked the FBI and the CIA to look into Tsarnaev in 2011.
Sen. Lindsey Graham, a Republican who serves on several committees including Armed Services, said Thursday he believes "ultimate blame" for the attacks goes to the Obama administration.
"The FBI and the CIA are, they have great people but, you know, we're going backwards in national security. Benghazi and Boston to me are examples of us going backward," he said.
But a ranking Democrat on a House intelligence subcommittee said Thursday he does not see an intelligence-sharing failure.
"This information was put in a database, it was shared among different agencies, it was shared with a joint terrorism task force, and that's exactly what should happen," U.S. Rep. Adam Schiff, D-California, told CNN.
"Some are racing to say that the FBI dropped the ball or the agencies weren't talking to each other, and that just doesn't seem to be the case," he added. Schiff is a ranking member of the Subcommittee on Technical and Tactical Intelligence.