WASHINGTON — U.S. intelligence agencies are investigating whether Edward Snowden’s leaks may be a Chinese intelligence operation or whether China might have used his concerns about U.S. surveillance practices to exploit him, according to four American officials.

The officials emphasized there’s no hard evidence yet that Snowden was a Chinese agent or that China helped plan his flights to Hong Kong and then to Moscow, directly or through a witting or unwitting intermediary. Rather, they are duty-bound to probe such a worst-case scenario for the United States, said the officials, who are familiar with the case and asked not to be identified to discuss classified intelligence.

President Barack Obama said the U.S. is working with other nations to gain custody of Snowden on espionage charges, as administration officials chastised China for letting him leave Hong Kong for Moscow and pressed Russia to turn him over.

Any suggestion that Snowden worked with China was “complete nonsense and extremely irresponsible,” China’s Foreign Ministry spokeswoman Hua Chunying said at a briefing Tuesday. Asked if Snowden’s case would derail Chinese-U.S. ties, Hua said the two countries have “always maintained close dialogue and contact.”

Snowden, the former government contractor who disclosed top-secret National Security Agency programs that collect phone and Internet data, intended to seek safe passage through Russia and “other states” to Ecuador, Julian Assange, founder of the anti-secrecy group WikiLeaks, told reporters Monday. He declined to name Snowden’s present location.

Russian President Vladimir Putin now has a choice to make, said one of the U.S. officials.

The Russian leader could return Snowden — perhaps only after Putin, a former KGB officer, gives his former intelligence colleagues time to question him — and defuse one dispute between the two countries. That would come at the risk of discouraging other would-be leakers or defectors from cooperating with Russia, the U.S. officials said.

The involvement of China and Russia raises questions about their relationship with Snowden and what information he may provide them, according to Jane Harman, president of the Wilson Center, a Washington-based policy research group.

“Clearly, he now is a pawn in a big-power game, and I think that game is way too big for him,” Harman, a former Democratic congresswoman from California who served on the House intelligence committee, said in an interview.

While U.S. counterintelligence investigations are mandatory in all cases in which top-secret information is made public without authorization, the U.S. officials said, their suspicions about Snowden began to take root when he fled to Hong Kong, which has a 1997 extradition treaty with the U.S. but is under the political control of China.

They grew deeper still when Snowden spoke publicly only about American cyber-attacks on China and Hong Kong even though he had access to information on espionage against other nations. In newly disclosed comments, Snowden, who previously worked for the Central Intelligence Agency, also said he sought out his most recent job with government contractor Booz Allen Hamilton in order to get more access to secrets.

“My position with Booz Allen Hamilton granted me access to lists of machines all over the world the NSA hacked,” Snowden told the South China Morning Post in a report dated Tuesday that the newspaper said was based on a June 12 interview. “That is why I accepted that position about three months ago.”

Suspicions were compounded by the timing of Snowden’s initial revelations on the eve of a summit in California between Obama and Chinese President Xi Jinping, where the American leader was planning to confront his counterpart about China’s commercial and government cyber-espionage efforts, said two of the U.S. officials.

Instead, China used Snowden’s revelations and evidence to put the U.S. on the defensive amid pro-Snowden demonstrations in the streets of Hong Kong that made it appear that denying a U.S. extradition request had popular support.

China filed a protest to the U.S., Foreign Ministry spokeswoman Hua said in a statement on June 23, and the government-controlled Global Times newspaper said Monday in an editorial that Snowden’s disclosures benefited the world, showing that China must catch up in network security.

Regardless of how Snowden came to land in Hong Kong and then Moscow, U.S. intelligence agencies must assume that China and Russia have debriefed Snowden and now have all the digital information he brought with him, said one of the officials.

Such a debriefing could have been direct or through intermediaries that Snowden may not have known were giving what they learned to a foreign intelligence agency, the official said.

As a result, all the officials said, American counterintelligence and security specialists have changed the electronic locks to virtually every classified intelligence compartment to which Snowden had authorized access or to which the material made public so far suggests he gained access.

Counterintelligence experts are also reviewing all Snowden’s communications and movements in recent years, to the extent that information on them is available from mobile-phone records, geolocation, keystroke-logging, interviews with co- workers and others and additional sources, the official said.

Snowden may have a technical road map of U.S. electronic surveillance systems and also know the names of spies and informants and the locations of safe houses abroad, ABC News reported, citing several officials it didn’t identify.

One pressing question is whether Snowden acted alone or got some of the material he’s disclosed from co-workers or from Chinese or other hacking activities. As a result, said two of the officials, everyone Snowden worked with while he held a top- secret clearance and everyone known to have crossed paths with him is under a microscope.

In particular, one of the officials said, investigators are searching for any evidence that Chinese intelligence officers might have played a role in his decision to flee in May to Hong Kong, where they could prevent his extradition to the U.S., debrief him and then send him on to Russia without being held legally accountable.

Albert Ho, a lawyer and Hong Kong legislator who said he was acting on Snowden’s behalf, said that if Snowden’s departure were orchestrated by the Chinese government, it would have been done behind the scenes so as not to aggravate Sino-U.S. ties.

“The Hong Kong government may not have had any role other than acting on instructions not to stop him at the airport,” he said.

The Hong Kong government said in a statement that the U.S. “did not fully comply with the legal requirements under Hong Kong law,” leaving the city “no legal basis to restrict Mr. Snowden from leaving.”

U.S. officials denied that, and White House spokesman Jay Carney said Hong Kong’s decision to let Snowden depart for Moscow “unquestionably” damages U.S. relations with China.

The U.S. officials said their doubts about whether Snowden is just a whistle-blower intensified when he flew from Hong Kong to Russia, where dissident journalists have been murdered, and WikiLeaks suggested that he would fly to Cuba and Ecuador, neither of which is known for press freedom, one official added.

Ecuador will “act upon our principles” in Snowden’s case, Foreign Minister Ricardo Patino said in Hanoi Monday. A decision by Ecuador to embrace Snowden would advance President Rafael Correa’s efforts to step out from the shadow of Venezuela’s late President Hugo Chavez and establish himself as the U.S.’s leading critic in Latin America.

Much of what WikiLeaks and others have said about Snowden’s possible itinerary, including previous talk of a flight to Iceland, has proved to be false, and the officials said they think Cuba may be a safer final destination than Ecuador or post-Chavez Venezuela if Snowden doesn’t stay in Russia.