When the police entered the trailer, they found 20-year-old Justin Stone and his girlfriend. Stone said he was a guest of the trailer’s owner, 23-year-old Jessica Quintana, who wasn’t there at the time. Stone was wanted on a probation violation from an earlier crime. So the police arrested him. When they later got a search warrant, the cops found what appeared to be the makings of a crude personal crystal-meth lab. (Stone later pleaded no contest to possession of drug paraphernalia.) Among the dozens of items they hauled away were three computer thumb drives–the small storage devices that plug into a USB port and can hold hundreds of megabytes of data.

The police plugged the memory sticks into their computers. They found more than 400 pages of classified documents downloaded from Los Alamos computers, some containing sensitive data on nuclear-weapons design. A quick check revealed that Quintana had until re-cently been employed by a contractor at Los Alamos. A file clerk who worked in the lab’s document-storage vaults, her job was to scan aging paper docu-ments into a modern digital format. The police called the FBI, which discovered another cache of nuclear documents: 456 paper pages, many stamped secret–restricted data.

Quintana has not been arrested or charged with any crime. Her lawyer, Steven Aarons, told NEWSWEEK that she took all the material home one afternoon in early August because she was under deadline pressure to create an index of what she had digitized. When she was finished, Aarons says, Quintana intended to destroy the material. “She wanted to take it to a shredder … She never did so.”

Recently, a series of humiliating security failures–vanishing computer hard drives, unauthorized downloads of secret data–have tarnished the lab’s once vaunted reputation. Those lapses were supposed to have been fixed. Panicked officials are now trying to determine how a low-level clerk was able to walk out of a high-security facility with hundreds of pages of nuclear secrets.

The brief answer: laxness and budget cuts. Though she had completed only one semester of college, in early 2005 Quintana was granted what the nuke world calls a “Q clearance,” which meant she had access to nuclear-weapons designs. She had further access to a category of information code named Sigma 15. This meant she could handle material detailing how to override the security locks on U.S. nuclear weapons. The vaults she worked in contained data from 50 years of nuclear tests.

Multiple layers of security supposedly protect such sensitive material. The lab’s hard drives are locked in cages to keep someone from plugging in, say, a thumb drive. To prevent temptation, clerks are supposed to work with a partner.

But those protections seem utterly to have failed. Aarons says that Quintana had a partner, but the company she worked for saved money by having them work separately. Quintana was able to insert the thumb drive she kept on her key chain into a caged computer because, Aarons says, the cages were never locked. Though employees were supposedly subject to searches, Quintana went home with the documents in her briefcase. Los Alamos officials, while declining to comment on specifics, issued a written statement saying, “The Laboratory is treating this matter with utmost seriousness.”

National-security officials will likely spend months investigating and putting new procedures in place. They are fairly certain that everything Quintana took has been recovered. Meantime, lab employees are getting a taste of what it’s like to work in a secure environment. The lab has barred workers from bringing in all manner of devices–no cell phones, no coffeemakers and certainly no thumb drives. Not that they would be of much use. The computers’ USB ports have now been sealed up with glue.