A Chinese scientist at Nasa has been pulled off a plane and arrested after attempting to leave the United States with a laptop and other computer data.
The FBI are investigating Bo Jiang, a contractor at the National Institute of Aerospace, after he boarded a plane at Dulles International Airport with a one-way ticket.
He had been working as a contractor and "research scholar" at Nasa on "high-tech imaging technology".
One US congressman said that if his work had been leaked it "potentially could be a direct threat to our country".
Representative Frank Wolf added that "the Chinese have the most comprehensive spying program in Washington that has ever been".
Wolf alleges that Nasa are not taking the threat seriously, though the situation is complicated because Wolf is chairman of the House Appropriations subcommittee that funds the agency.
Jiang admitted he had a mobile phone, a memory stick, an external hard drive and a laptop when he tried to leave the States, the FBI said.
Special Agent Rhonda A. Squizzero added:
"However, during the search, other media items were located that Jiang did not reveal. Such items found include an additional laptop, an old hard drive and a SIM card."
It is not known, or has not been revealed, what data was on the devices.
Nasa said it was reviewing "a potential security breach" but did not elaborate.
"The agency takes any allegation of a security violation very seriously," it said.