Federal investigators are frantically trying to determine what happened to a missing laptop computer that contains sensitive data on as many as 100 Drug Enforcement Administration investigations around the country, including a wealth of information about many of the agency's confidential informants, NEWSWEEK has learned. The computer was first reported stolen three weeks ago by an auditor for the Justice Department's Office of Inspector General, which was conducting a routine review of DEA payments to informants. The auditor told police the laptop had been stolen from the trunk of his car while he was at a bookstore coffee shop in suburban Washington. But when investigators confronted the auditor last week and questioned his account, the auditor changed his story, saying he had accidentally damaged the computer--then destroyed it and threw it away in a Dumpster to avoid embarrassment. Investigators are seeking to verify his new account. Either way, DEA agents are "livid," said one senior law-enforcement official who noted that, although the computer didn't contain informants' names, it included more than 4,000 pages of case-file data, including enough details about the informants' work that it could allow drug traffickers to figure out who they are. "This is a sin in our business," the official said. The incident is a particular embarrassment for Inspector General Glenn Fine's office, which has taken on an expanded watchdog role under Attorney General John Ashcroft. Only two years ago, the IG issued a blistering report criticizing Justice agencies, including the DEA and the FBI, for failure to maintain adequate controls on sensitive items--including their laptop computers.