SAN FRANCISCO -- Lawrence Livermore National Laboratory failed to properly track cocaine, amphetamines, opium and black tar heroin that undergoes forensic evidence testing and other uses, leaving personnel unable to determine if the drugs had been misused or misappropriated, according to a federal report released Thursday.

Some drugs were missing, while opium and black tar heroin were found in greater amounts than lab records showed were

purchased legally, the Energy Department's inspector general said in the report.

"I don't think that the inspector general's office said there was anything nefarious going on here," lab spokesman Jim Bono said. "What they pointed out was less than stellar record-keeping. And we agree."

Employees at Livermore, one of the federal government's top science labs, handle as many as 42 different kinds of controlled substances. Illicit drugs are kept at the lab mainly to use as controls when testing whether drugs seized by law enforcement agencies are what they appear to be.

The lab is also officially registered to use drugs for biomedical research and in its health clinic. Workers are required under federal law to track the use closely, with penalties that can include fines up to $10,000 per violation.

The report, however, said employees failed to adequately monitor at least six of the 42 varieties of drugs on site. It noted

quantities of an amphetamine known as MDA had disappeared between 2004 and 2009, and that five times more opium and 20 times more black tar heroin was found at the lab than records accounted for.

"Livermore was in possession of additional quantities of high-risk, controlled substances without any documentation showing that they existed," the report said.

Sloppy record-keeping meant that "responsible personnel were not in a position to determine if controlled substances were purchased and then misused or misappropriated," it added.

The inspector general's report said records showed the lab had 12 milligrams of heroin on hand. But the actual weight of the sample was 244 milligrams.

Bono said scientists at the lab believe the dramatic weight increase may have simply resulted from the drug sample absorbing moisture from the air.

In addition, inspectors found records at the lab for one bottle of cocaine hydrochloride but no references to the amount inside. There were also references to two additional shipments of cocaine hydrochloride in 2006, but it was unclear if those shipments ever arrived.

Bono said the lab keeps a gram or less of all but two of the substances, and all controlled substances are kept in a safe. Meanwhile, drugs sent by law enforcement are immediately destroyed during the forensic testing, he said.

Officials with the Energy Department's National Nuclear Security Administration, which operates the labs, agreed that a more rigorous tracking system was needed at the lab.

Associate NNSA Administrator Gerald Talbot Jr. wrote in a letter that Livermore managers immediately began changing inventory procedures after the inspector general reported problems last month.

Talbot also noted that Livermore's analytical lab has not purchased any drugs for forensic science in at least two years, but inspectors said missing records meant there was no evidence that was true.

Lawrence Livermore has long served as one of the nation's key labs for nuclear research. More recently the lab has focused on measures to counter possible chemical and biological terrorist attacks.

The lab has faced criticism for lapses in the past.

In the 1980s, six Livermore lab workers were arrested and successfully prosecuted for making drug deals in in a restricted plutonium research building.

In 2005, the U.S. Defense Nuclear Facilities Safety Board found the lab was storing plutonium -- the main material used for making nuclear bombs -- in food and paint cans. The lab in 2007 was fined $450,000 after another federal agency found that a former scientist sent two open vials of anthrax across the country.

"Livermore Laboratory has a history of accounting problems with both nuclear materials and biological agents," said Marylia Kelley, executive director of Tri-Valley CAREs, a watchdog group that monitors the lab. "We're dismayed but not surprised that they have an accounting problem with the controlled substances."