The New York Times has reported that Wen Ho Lee may have downloaded huge amounts of data from a top-secret computer system at Los Alamos, New Mexico, compromising nearly every nuclear weapon in the U.S. arsenal.
CBS News Correspondent Sharyl Atkisson conducted an exclusive interview with nuclear scientists about security at U.S. labs.
The scientists who spoke with Atkisson work at Lawrence Livermore in California, one of the labs where intelligence officials say the Chinese stole sensitive weapons data in recent years.
They say in the last half of the 1990's, there's been a significant change in the working atmosphere, a loosening of security.
The two men who have the highest security clearance, a Q-clearance, want their identities protected. Hugh DeWitt had a Q-clearance for four decades, and now conducts unclassified research.
The men say in the early 90s, workers without a Q-clearance began getting access to buildings where classified work is done. And still today, the only security keeping non-Q-cleared workers away from sensitive areas is often no more than a keep out sign.
Â"There is a door on one facility that says Â'Q-onlyÂ' and itÂ's up to the person if theyÂ're not a Q and they are in the limited area to not go in that building,Â" said one man.
It is the same story inside the buildings and on elevators that lead to classified floors.
Â"There is no physical impediment, either a barrier, swiping station, a guard, or anything like that,Â" he said.
And when scientists need to discuss classified material, there is often no special security check, just an honor system. Workers who donÂ't belong are supposed to leave the room. It is a system that presumes all the employees are honest, and requires them to self-patrol classified areas.
Self-patrolling became tougher a few years ago when security badges were re-designed.
Â"Now, low-clearance badges look much like the highly classified Q-badges,Â" DeWitt said. Â"I think it struck most people as a bad idea.Â"
But the biggest threat may lie in the ability of hundreds of Q-clearance workers to simply carry out reams of secret documents.
Â"It would be very straightforward for such a person to smuggle documents, classified documents, outside of Livermore lab and get them into the hands of foreign agents by fax, of u.s. mail, even,Â" said the anonymous worker.
That is because Q-cleared scientists, or anyone using their badge and id number, can get in and out of classified areas without ever encountering a guard.
Â"It would be nothing more than coming on off hours, swiping your badge through an unmanned gate, stuffing your briefcase full of classified information and then going back out through that turnstileÂ… never see a person,Â" he said. Â"Go back in your car, drive off -- with a very significant amounof classified material.Â"
Security and intelligence officials at the labs and the energy department confirm the scientists' accounts. One congressional investigator told CBS News the U.S. has never been able to figure out how China stole huge amounts of weapons data, but that the scientists' stories provide the best insight yet into how easily lab security can be breached.