IBM said on Wednesday that a contractor lost more than one tape containing identifying information on current and former IBM employees.

The company isn't saying how many employees are affected by the lost data or how many tapes are missing, according to Fred McNeese, an IBM spokesman. He added that the company doesn't believe the tapes were stolen.

"If anyone has the tapes, we don't want to give much detail about them," he said.

McNeese, in an interview with InformationWeek, said IBM has offered a reward for the return of the tapes or information about their whereabouts. The company ran ads in several local New York papers seeking the tapes' return and offering a reward of an unspecified amount. "So far, the ads have failed to find the tapes for us," he said, but he wouldn't say how many responses IBM received.

The tapes were lost while in route to a long-term storage facility, said the spokesman. An unnamed long-time IBM contractor was transporting the tapes when they were lost near the intersection of Interstates 287 and 684 in Westchester County, N.Y., according to McNeese. He wouldn't say if the tapes were lost during an auto accident of if they somehow simply fell out of the vehicle.

"It was an inadvertent thing," he added. "We're not being specific about the incident. We still do not know what happened to those tapes."

The contractor who lost the tapes is still employed by his firm.

The tapes, which were lost on Feb. 23, contain information on IBM employees -- those who are still working for the company, along with retirees, people who left for other jobs, and people who might have left the company and then returned. The tapes hold employment data on them, including names, addresses, birth dates, Social Security numbers, and beginning and end dates of employment, McNeese said.

The spokesman wouldn't say if the lost information was encrypted. He would only say that "various tapes had different levels of protection."

McNeese said local and state law enforcement agencies were called in to investigate. The company began to notify those affected about the loss in April. "It took us a while to determine what was on the missing tapes, and then it took a while to line up the credit monitoring and to begin notifying people," he added.

IBM is offering those affected by the loss a free year's worth of credit monitoring.