ST. LOUIS -- The St. Louis Police Department is changing the way it handles seized vehicles after a three-month internal investigation found no criminal conduct but raised ethical concerns, officials said Friday.

For years, the department contracted with S&H Towing to take vehicles seized in arrests. If not claimed, the company sold those vehicles through its subsidiary, Parks Used Auto Sales.

The investigation found that Parks allowed some people to take the vehicles for test drives that lasted several days, even weeks or months. Among those people were police officers and the daughter of chief Joe Mokwa. Mokwa told investigators he alerted the Board of Police Commissioners as soon as he learned of the practice.

The police board asked the law firm Armstrong Teasdale to investigate. As a result of the investigation, the department ended its contract with S&H.

"The biggest issue is public trust and public confidence," Chris Goodson, president of the Board of Police Commissioners, said at a news conference. "We don't want it to seem that our officers are getting special privileges."

The investigation also uncovered a flaw in a computer system that lists seized vehicles. Once taken, they are listed in the Regional Justice Information System as "Held for Evidence" until the circuit attorney's office orders the vehicles released, changing the classification to "canceled."

Then, the owner has 30 days to pay towing and storage charges. If not, the vehicle becomes the property of the tow firm.

It was determined that 849 cars initially held for evidence were never changed to "canceled" in the computer system. As a result, an officer stopping a car once held as evidence could get the wrong impression that the car should still be in police custody when, in fact, it had been legally sold.

The investigation determined a staff member simply failed to enter the changes in the computer. That worker was reassigned to a different job and replaced by two others to help lessen the work load.

Investigators cleared Mokwa of any wrongdoing. He became aware of the problem after learning early this year of a 2006 traffic stop involving his daughter in Warren County. She was driving a car previously seized by St. Louis police and left unclaimed. Parks loaned her the car for several months. Because of the computer error, the car was incorrectly listed as "Held for Evidence" when she was stopped.

Police said Mokwa immediately notified Goodson and instructed the towing company to end the practice of loaning out cars to his relatives. Mokwa also asked the board to conduct the internal investigation.

An official with Armstrong Teasdale said the cost of the investigation has not been determined.