A double-decker bus collided with a tree in southern Thailand, killing at least 14 people and injuring 32 others, according to the Thai police on Tuesday.

The bus was heading from Bangkok to the far south of the kingdom when it hit the tree in the coastal Prachuap Khiri Khan province on Monday evening.

Photos published by local media showed the front part of the bus split into two sections due to the force of the collision, with the tree in between.

For his part, Arnon Tangtu, a police investigator in the Huai Yang area of Prachuap Khiri Khan, told Agence France-Presse, "According to a preliminary investigation, 14 people were killed and 32 others injured," adding that the investigation is ongoing.

He added that the cause of the accident is not yet clear, but the police suspect that the driver, who was seriously injured but is still alive, may not have had enough sleep.

He also said, "We are cooperating with the hospital to check the alcohol level in his blood."

The police are still investigating whether all the deceased were Thai nationals.

Thailand has one of the highest rates of road accidents in the world, with around 20,000 people killed annually, according to the World Health Organization.