A Chester County police chief has been disciplined for allowing his 16-year-old son to drive a township police car in an episode that ended with a crash, and then for failing to tell township supervisors..

Tredyffrin Township Police Superintendent Andrew Chambers, who has headed the department since 2008, was suspended for four days without pay in response to the Nov. 23 incident, Township Solicitor Vincent T. Donohue said Thursday.

Donohue said Robert W. Lamina, the supervisors' chairman, received an anonymous letter in the mail the weekend of Dec. 3 that he did not read until the evening of Dec. 4, because he had been out of town.

Chambers called Lamina on Dec. 5 to tell him about the accident, and Lamina told him he had received the letter, Donohue said. He said an investigation was begun and about 15 people were interviewed.

They included 11 or 12 officers who participated in the training exercise during which the accident occurred as well as people involved in the towing and repair of the vehicle, which Chambers paid for, Donohue said.

He said Chambers' son, who has a learner's permit, was behind the wheel of a police vehicle in the company of an instructor on a closed driving course in Bridgeport used regularly for police training.

The teen "lost control of the vehicle, which slid off the road and collided with a small tree, causing minor damage to the front push bumper," Donohue said. Other than a small cut sustained by the trainer in the car, no one was injured. The vehicle got a flat tire while being extracted by a tow truck, Donohue said.

Because the crash occurred in a fenced, locked area, there was no requirement to report it to local police, Donohue said. "The delay in reporting the incident" to the seven-member board was factored into Chambers' punishment, Donohue said.

"The township is disappointed with Superintendent Chambers' uncharacteristic lapse in judgment and is glad no one was seriously injured," a statement from the township supervisors said. "Superintendent Chambers has fully and openly admitted the facts and very much regrets his conduct. . . . [He] has had an exemplary, unblemished record in his 30 years of service to the residents of Tredyffrin Township, and the supervisors continue to have full confidence in his ability to perform his duties."

Donohue said the statement would be posted on the township website and would be read aloud at Monday night's supervisors meeting. He said Chambers would return to work Wednesday.

Contact staff writer Kathleen Brady Shea at 610-696-3815, kbrady@phillynews.com, or @brandywinebits on Twitter. Read her blog, "Chester County Inbox," at www.philly.com/chescoinbox.