KYOTO (Kyodo) Three people died and seven others were injured in an accident Monday morning involving 12 vehicles on an expressway in Uji, Kyoto Prefecture, police and firefighters said.

The accident on the Keishi Bypass occurred after a driver stopped to rescue a man, apparently a pedestrian, who was lying in the fast lane after being hit by a car, causing 10 other vehicles to stop behind him, according to police.

Then a tank truck smashed into the rear of the line of cars, causing a multiple crash. One of the vehicles caught fire, police said. Two of the three dead were in the burned car, while the other was a man in a car sandwiched between two trucks.

They arrested Koichi Kitamura, 35, the driver of the tank truck, on suspicion of professional negligence resulting in death.

Investigators found a walker near the man in the fast lane, who was only identified as being from the city of Kyoto and aged 50. They suspect he mistakenly got on the bypass, adding he sustained serious injuries.