Officials for the city of Kansas City revealed Saturday that they cannot find 26 computer tapes containing taxpayer data from the Internal Revenue Service that were delivered to City Hall in August.

The officials said they aren't exactly sure what's on the tapes, which were sent to Kansas City to help the city calculate and collect its annual 1 percent city earnings tax. IRS officials declined to comment.

Officials said they are trying to retrace the path of the tape shipment, which was supposed to have been delivered more than four months ago. An investigation began when the tapes were not returned to the IRS in a timely manner; Kansas City officials said they have no record that the tapes were ever delivered to the city's Finance Department, and they did not learn of the lost tapes until the end of December.

With city officials in the dark and the IRS not talking, it's impossible to say how many taxpayers might be affected by the data loss or what personal data might be missing. Experts say the information shared between municipal governments and the IRS could include name and address, Social Security numbers, bank account numbers, and/or employer information.

City officials said they didn't suspect foul play, and that the data would require "special equipment and software" in order to be read. But observers say the IRS typically uses 800 MB cartridge tapes and nine-track real tapes, and that unless the data was encrypted, it would not be hard to find the equipment required to view the data.

Kansas City officials say they are cooperating with the Treasury Department's efforts to find the tapes, which included a search of employees' offices.

IRS officials declined to comment on when or whether they plan to inform the affected taxpayers of the data loss.

— Tim Wilson, Site Editor, Dark Reading