TAIPEI, March 18 (Xinhua) -- A preliminary investigation into a fire that destroyed several police motorcycles here early Wednesday morning has not yet found evidence of human involvement, but no cause has been ruled out, according to local police.

The fire, which started at around 3:00 a.m. in the parking lot of Songshan police station in Taipei City, destroyed 11 police motorcycles and partially damaged two other motorcycles and another two police vehicles, according to Lin Chi-tien, deputy head of the Taipei City Police Department's Songshan Precinct.

Lin told Xinhua that preliminary investigation by the police department and fire department did not uncover lighters or other incendiary materials nor any solid or liquid combustibles at the scene. Scrutiny of footage from nearby cameras has not revealed any suspicious person or vehicle.

However, he said it is difficult to rule out arson as the cause of the blaze at this stage as the investigation is still ongoing.

The exact cause is expected to be determined within a week, according to Lin.