The female driver who killed four and injured 13 pedestrians in a car accident in downtown Hangzhou late last month was found to be wearing slippers while driving and had mistaken the gas pedal as the brake, police said on Thursday.

Five of the injured are still in hospital, with one of them being in critical conditions.

The driver, who is surnamed Chen, lost control of her vehicle when crossing an intersection in Hangzhou, capital of east China's Zhejiang province, in the evening of July 30, and ploughed into the crowd at the speed of 132 kilometers per hour.

Evaluation centers employed by the traffic authority have stated that the woman does not have mental problems and was not under the influence of alcohol or drugs during the incident.

Chen was placed under police custody after receiving medical treatment on July 31.

Yu Dingzhang contributed to this story.