Thirty-five of the missing handguns, rifles, Tasers and other weapons were stolen, as were 50 laptops, the internal audit found. Two of the stolen weapons were used in crimes.
The audit by Justice Department Inspector General Glenn A. Fine found "inadequate" oversight of weapons and laptops resulted in "significant rates of losses" at the Bureau of Alcohol, Tobacco, Firearms and Explosives.
"It is especially troubling that that ATF's rate of loss for weapons was nearly double that of the FBI and DEA, and that ATF did not even know whether most of its lost, stolen, or missing laptop computers contained sensitive or classified information," he added.
In a Sept. 10 letter responding to the audit, ATF acting Director Michael J. Sullivan said his agency "agrees or partially agrees with most of the recommendations."
"We are revising our procedures of reporting losses of weapons or laptops," Sullivan said.
The audit looked at ATF's inventory of weapons, laptops, ammunition and explosives between Oct. 1, 2002 and Aug. 31, 2007.
It found that ATF lost three times more weapons each month than it had in a similar 2002 audit by the Treasury Department, which used to oversee the agency. It also lost 50 times as many laptops as reported in the earlier audit.
Of the 76 weapons, 35 were reported stolen, 19 lost and 12 missing from inventories, investigators found. Of the 418 missing laptops, 50 were stolen, 8 lost and 274 could not be found during inventory. Another 86 laptops were unaccounted for because ATF had either destroyed or lost documents showing where they were, the audit concluded.
Two weapons reported stolen were used to commit crimes. In one instance, a gun was stolen from an ATF car parked outside the agent's home and later used to shoot through the window of another residence, the audit found. In the other, a stolen ATF gun was taken from a burglary suspect.
Additionally, ATF employees did not report 13 of the 76 lost weapons, or 365 of the 418 missing laptops, to internal affairs as required. ATF officials also did not report much of the lost equipment to the Justice Department.
Investigators could not conclude what was on 398 of 418 missing laptops - except that few were encrypted. That means any sensitive material on the laptops could have been exposed.
Moreover, "we found that ATF did not regularly attempt to determine whether the lost, stolen or missing laptop computers contained sensitive or classified information," the audit said.
But few - only 18 of 7,500 - ATF laptops were authorized to hold classified information.
Compared to weapons loss rates for the FBI and Drug Enforcement Administration, the ATF misplaced almost twice as many guns. The audit found that the ATF lost .52 weapons per 1,000 employees, compared to .29 at the FBI and .28 at the DEA.
Fine's investigators concluded there were proper controls and oversight of explosives in ATF's possession, and good security for ammunition. However, nine of 20 ATF field offices surveyed did not have proper accounting methods for ammunition.