A boat caught fire inuring 18 tourists while it was taking them to the notorious Thai 'death island'.

The vessel had reached five nautical miles off the coast of Chumphon province while heading to Koh Tao island when an explosion was heard from the engine room on July 20.

A few minutes after the loud bang was heard, fire quickly spread and soon engulfed the cabins.

Out of the 21 tourists on board, 18 were injured, six of whom were in critical condition, after a rescue operation done by officers. Two crew members were also injured.

Chumphon Regional Port Officer Director Yuttachai Chitareerat said: ‘The injured were rushed to the Paknam Chumphon Hospital upon reaching the port. Six of them were seriously injured.'

The boat, which had a capacity of 35 people, had only left the pier five minutes earlier when there was an explosion. It was taking the tourists to the island for a diving trip.Burning debris was washed ashore, which was put out by local fire volunteers.

Provincial governor Chotinarin Kerdsom later went to the area to inspect the site. He has ordered an investigation into the incident.

The official said: 'All of the passengers were wearing life jackets. They were rescued and taken onto a nearby boat before going to hospital.

'We believe the accident was caused by an engine problem.'

The fire reportedly started at the boat's engine room but the cause of the explosion was unclear. Investigations on the incident are ongoing.

Many of the ferries that leave the mainland on Chumphon to reach Koh Tao have been out of services for more than two years, due to the travel restrictions imposed by the recent pandemic reducing tourism.

Koh Tao in southern Thailand was dubbed 'death island' following a spate of unsolved murders and deaths.

Most notoriously, British backpackers Hannah Witheridge and David Miller were bludgeoned to death on a beach before two Burmese laborers were framed by corrupt Thai police and jailed for life - while the real killer went free.