An elevator in the 13-story Itabashi Ward office in Tokyo inadvertently ascended until it hit the top of its shaft in January, apparently due to a maintenance error by Nippon Otis Elevator Co., the ward and the company said.

Nobody was in the elevator at the time. The impact was strong enough to dislodge a cover over the lighting and floor tiles inside the elevator.

The company and ward said the Jan. 10 incident was not reported to the Land, Infrastructure and Transport Ministry because there were no injuries.

The building was completed in 1987 and all nine elevators were installed and maintained by Nippon Otis, which said it routinely checks them.

For the elevator in question, Nippon Otis disassembled and cleaned the brakes on Dec. 23, during which an employee apparently applied excessive amounts of the wrong type of lubricant, causing the brakes to lack sufficient grip.