SEOUL, South Korea (AP) — Two people were killed and 18 others were injured Thursday after a truck plowed into pedestrians at an outdoor market in South Korea’s Bucheon city, fire and police officials said.

Police are questioning the unidentified truck driver in his 60s who was not under the influence of alcohol or drugs, said Son Byeong-sam, a police official in Bucheon, near the capital city of Seoul.

Park Geum-cheon, an official at Bucheon’s fire station, said witnesses told investigators that the vehicle initially reversed about 28 meters (92 feet) before driving forward 150 meters (492 feet), hitting pedestrians on the way.

The driver claimed his vehicle had malfunctioned and that officials were reviewing security camera footage, he said.

Two victims were pronounced dead at a hospital, and 11 of the 18 injured sustained serious injuries. Officials did not immediately say if any of the injuries were life-threatening.

Photos from the scene showed the truck jammed into a storefront in a jumble of debris, including toppled boxes, clothing and broken signboards. The front left side of the truck was mangled and its windows were shattered.

Officials later removed the vehicle from the scene to investigate the crash.