Police raided the headquarters of Mitsubishi Motors on Tuesday, expanding their investigation into a fatal accident in which a wheel came off a truck and crushed a pedestrian, Associated Press (AP) reported.

AP noted it was the second time in three months that police have searched the company on suspicions of professional negligence after wheels repeatedly fell off of Mitsubishi trucks and, in one case, caused a death and two injuries.

According to the report, police reportedly said their officers first raided the company’s Tokyo headquarters in October and, on Tuesday, expanded their search to several other locations, including the Tokyo offices of Mitsubishi’s bus unit, Mitsubishi Fuso Truck and Bus Corp., and a plant in nearby Kawasaki.

After the January 2002 accident, in which a woman and her two sons injured when a wheel from a Mitsubishi trailer hit them as they walked along a footpath in Yokohama, west of Tokyo, investigators found the hub linking the axle to the wheel was broken, AP said.

Mitsubishi Motors has reportedly denied any error in the production and design of the vehicles but has admitted that faulty checks led to the accident which could have been avoided if the bolts were tightened properly.

According to Associated Press, the national Yomiuri newspaper said in its Tuesday evening edition that a police research institute analysis of the hub involved in the Yokohama accident found “no structural defect” though officials refused to confirm the report.

A Mitsubishi Fuso spokesman told AP that 50 cases of unloosening wheels were reported, but there were no further reports of injuries or significant damage.

AP cited local media reports which said that police believe as many as 30 cases were reported before the accident that prompted Mitsubishi to implement extra safety measures.

AP noted that, four years ago, Mitsubishi Motors said it systematically hid vehicle defects to avoid recalls for more than two decades – the disclosure came after investigators found a stack of unreported driver complaints in a company locker following an anonymous tip and the company later recalled more than a million vehicles.