In a heavily redacted report obtained by The Kansas City Star through a Freedom of Information Act request, the Treasury Department's inspector general for tax administration said the city failed to follow "proper safeguards for protecting federal tax return information."

The tapes were delivered to City Hall in August 2006 to help revenue officials make sure people living or working in Kansas City are paying the 1 percent city earnings tax.

City officials said they realized the tapes were missing in late 2006, touching off the investigation that began on Dec. 19, 2006, and lasted until Nov. 1, 2007. The tapes have never been found.

"The investigation revealed the city did not follow and was not following the proper safeguards for protecting federal tax return information," the inspectors wrote.

The information released to The Star and published in a story Saturday did not elaborate on the city's mistakes. Most of the information in the 42 pages provided to the paper was blacked out, and the agency said it wasn't handing over another 105 pages because that "could impede its law enforcement activities."

The IRS has never said what was on the tapes, how many taxpayers may have been affected or whether taxpayers would be told of the lost information.

Amy Jones, a disclosure officer for the inspector general's office, told The Star that the agency typically withholds information such as witness interviews and investigation techniques.

"The information was compiled for law enforcement purposes and the privacy interests of the third parties outweighs the public's interest in having the information released," the agency said.

According to the report, a copy was provided to the IRS but not to the U.S. attorney's office.

IRS spokesman Michael Devine declined to comment to The Star, citing federal disclosure laws covering taxpayer information. He did not immediately return phone and e-mail messages left by The Associated Press on Saturday.

City spokeswoman Mary Charles said the city has tightened its policies for securing taxpayer information but is still waiting for the IRS to share its concerns.

"This is an important document for us to have," City Manager Wayne Cauthen said. "We cooperated with the investigation ... but they haven't shared anything with us, either."

City officials added that the tapes are unreadable without special equipment.

Charles said the city is no longer receiving IRS information but is sharing information with the state and Jackson County to make sure workers and residents are paying the earnings tax.