HONG KONG (CNN) -- The man who acknowledged leaking details of classified U.S. surveillance programs seemed to melt into the streets of Hong Kong as FBI investigators worked Tuesday to build a case against him and criticism of the programs continued to mount.
Edward Snowden, 29, apparently checked out of his Hong Kong hotel room Monday and has not been seen since. A reporter who helped develop stories from the information Snowden leaked said he believes the former contractor for the National Security Agency remains there.
U.S. authorities are preparing charges against Snowden, a law enforcement source told CNN on Tuesday. But they are not imminent, the source said.
As authorities investigated, the first civil lawsuits were filed against federal officials, arguing that the surveillance programs are unconstitutional.
Snowden is a former computer security contractor who acknowledged in a Guardian newspaper interview published Sunday that he gave classified documents about U.S. surveillance of telephone and Internet traffic to journalists.
The FBI has been investigating the leaks, but it was unclear Tuesday how far along the agency was.
A federal law enforcement source told CNN on Monday that the investigation will include searches of Snowden's home and efforts to interview his girlfriend, relatives, co-workers and friends.
The official did not know if the FBI would attempt to contact Snowden overseas and ask if he would agree to a voluntary interview, or if the agency would wait until other evidence had been gathered.
Snowden himself told the Guardian that he expects to be charged under the Espionage Act and said he traveled to Hong Kong in hopes that state's commitment to free speech would prevent his extradition to the United States.
Snowden's disclosures have fueled new debate about the U.S. government's collection of records of domestic telephone calls and overseas Internet activity in the global hunt for terrorists and criminals.
Civil liberties advocates say the measures are unacceptable intrusions. But supporters say they are legal and have yielded evidence that has helped stop terror plots.
White House spokesman Jay Carney said Tuesday that the measures "strike a balance between our security interest and our desire for privacy."
"There has to be some modest concession to the need for information as we pursue terrorists who mean to do harm to the country and take the lives of Americans," Carney said. "But ... we need to make sure that the programs we have in place are properly overseen, that they are legal, that they are authorized by Congress and they are authorized by the courts, and that is the case here."
But at least two civil lawsuits have been filed so far against federal officials, arguing that the collection of phone records is unconstitutional and calling for a judge to block the measure.
"The practice is akin to snatching every American's address book -- with annotations detailing whom we spoke to, when we talked, for how long, and from where," the American Civil Liberties Union and several other groups said in a federal lawsuit filed Tuesday. "It gives the government a comprehensive record of our associations and public movements, revealing a wealth of detail about our familial, political, professional, religious and intimate associations."
A Philadelphia couple who allege they were singled out for electronic surveillance because of their criticism of the U.S. military filed a $3 billion class action lawsuit, claiming their privacy and free speech rights were compromised.
Support and criticism
In political circles, fallout from the revelations surged, with the administration facing a steady stream of criticism and support from allies and enemies alike.
House Speaker John Boehner, who has frequently clashed with President Obama, stood by him Tuesday on ABC's "Good Morning America."
"The president outlined last week that these are important national security programs that help keep Americans safe and give us tools that help fight the terrorist threat we face," Boehner said. "The disclosure of this information puts Americans at risk. It shows our adversaries what our capabilities are. And it's a giant violation of the law."
But Boehner's fellow conservative, former U.S. Rep. Bob Barr of Georgia, said potential charges against Snowden are little more than a sideshow.
"The real question that the American people and the Congress need to be focusing on is not did Edward Snowden violate the law, but did the U.S. government violate the law?" Barr told CNN. "That is the most troubling and much more important question for the American people and for the Congress."
Then there was Democratic Sen. Ron Wyden of Oregon, who blasted Obama's top intelligence official Tuesday, saying that James Clapper failed to shoot straight during a March congressional hearing.
"One of the most important responsibilities a senator has is oversight of the intelligence community," Wyden said. "This job cannot be done responsibly if senators aren't getting straight answers to direct questions."
In March, Wyden asked Clapper whether the NSA collects "any type of data at all on millions or hundreds of millions of Americans?"
"No sir," Clapper said.
On Saturday, Clapper told NBC News that he "responded in what I thought was the most truthful or least most untruthful manner."
He told NBC that he had interpreted "collection" to mean actually examining the materials gathered by the NSA.
He had previously told the National Journal that he had meant that "the NSA does not voyeuristically pore through U.S. citizens' e-mails," but he did not mention e-mails at the hearing.
Clapper's office had no immediate comment on Wyden's statement.
Concern over security clearance
Criticism also began to emerge over how Snowden, a low-level computer technician working for a private contractor in Hawaii, was able to have access to such highly classified information.
Sen. Barbara Mikulski, D-Maryland, said Tuesday that "people are asking why does a kid who couldn't make it through community college can make $200 grand a year and be exposed to some of our most significant secrets."
Snowden last worked for the computer consulting firm Booz Allen Hamilton.
The company fired him Monday after less than three months on the job for violations of company policy and its code of ethics. Despite what he had said was a $200,000 salary, the company said he earned $122,000.
U.S. intelligence officials say the NSA, CIA and other intelligence officials are reviewing security measures in light of the leaks, examining how Snowden had access to so much information and weighing whether changes should be made.
They are also looking at the contractor piece of the picture, although the officials say security clearances are no different for contractors than they are for staff employees.
Michael Hayden, who once led both the CIA and NSA, told CNN the leaks showed a failure of security, not a contractor issue.
"If you're going to give anyone access to your database, it's still your database," he said, "and you have to assume responsibility for the vetting process of the contractors involved."
Hayden said he was surprised this kind of data would have been available to Snowden.
"I'm more surprised that a low-ranking fellow, working apparently on a NSA contract in Hawaii, gets access to such a sensitive program," he said.
Uncertainty over next move
While Snowden said he fled to Hong Kong in hopes of avoiding extradition, what's next for him remains unclear.
Although Hong Kong is part of communist-ruled China, the former British colony has a separate system of government that allows a free press and tolerates political dissent.
But legal experts say Hong Kong's extradition treaty with the United States could make it hard for Snowden to successfully fight any proceedings against him unless he is able to prove, for example, that any charges against him are politically motivated.
Patricia Ho, a lawyer with Daly & Associates in Hong Kong, whose firm has handled asylum and refugee claims, said that given Hong Kong's lackluster track record on granting asylum, she was surprised that Snowden had lauded the territory for its commitment to civil liberties.
"Within China itself, Hong Kong has better civil liberties, but I couldn't see the Hong Kong government granting him asylum given their present practices," she said.
On Monday, the office of Russian President Vladimir Putin's spokesman tweeted that U.S. officials had broken the law with the surveillance programs, making Snowden a "human rights activist."
Spokesman Dmitry Peskov told CNN that Russia would consider an asylum request from Snowden, but has not received one.
Google on Tuesday asked for permission to publish details of requests for information under the Foreign Intelligence Security Act. It wants to regain the trust of users after initial assertions that it and other companies were providing the NSA with direct, unrestricted access to data stored on their computers.
"Assertions in the press that our compliance with these requests gives the U.S. government unfettered access to our users' data are simply untrue," the company said in a letter to Attorney General Eric Holder and FBI Director Robert Mueller.
But government laws demanding secrecy about the requests "fuel that speculation," the company said.
"Google's numbers would clearly show that our compliance with these requests falls far short of the claims being made," the company said. "Google has nothing to hide."