Four people were killed, one a monk, and five others injured when a van taking them on a pilgrimage rear-ended a trailer truck in Nakhon Sawan on Wednesday morning.

The crash happened on Highway 11 in tambon Donkha.

Police received a report of the accident about 7am. 

An 18-wheel trailer truck was parked on the roadside with rear end damage. 

A passenger van was stopped on the road nearby. It was badly damaged with its roof torn off and lying on the road. 

Four people were dead at the scene, trapped in the wrecked van - two men and two women. One was a Buddhist monk. Five other injured passengers had already been rushed to hospital.

The trailer truck driver was waiting at the scene. 

He told the officers he was on his way to pick up a load of sugarcane. He slowed down, intending to park on the roadside, and heard a loud crash as something hit the truck from behind. 

He said an injured monk told him the driver had looked sleepy before the crash. 

The van was carrying monks and lay followers from Wat Phra Dhammakaya on a pilgrimage to a branch of the temple in Phichit province. 

Police said the van driver may have fallen asleep at the wheel.