BANGKOK (AP) — Two passenger trains collided north of Thailand's capital, injuring more than 20 people, authorities said.

It was not immediately clear what caused the wreck late Thursday in the central province of Ayutthaya, just north of Bangkok.

The State Railway of Thailand posted a statement on their Facebook page saying a northbound train crashed into the rear of another train.

Police Col. Nateepat Thammaratsophon put the number of injuries at 22. He described most of the injuries as minor but said two people were in critical condition — one of the train's drivers and a mechanic.

Most of the remaining passengers were able to leave the site on another train provided by the state railroad company, Nateepat said, adding that soldiers and state officials helped transport other people from the site as well.

Nateepat said both trains had departed Bangkok and were headed north when one rear-ended the other in Ayutthaya's Phachee district. "We are still investigating the cause of the collision," he said.

The accident was the latest to hit Thailand's transportation industry.

Earlier Thursday in the southern province of Trang, Thai media reported that a pickup truck driver was killed when his vehicle crashed into a passing train. On Tuesday, a passenger train collided with a truck during heavy rains near the northern city of Chiang Mai, killing seven construction workers in the truck and seriously injuring another, police said.