A British tourist is missing in Thailand after the tour boat she was travelling on, the Davy Jones Locker, caught fire off the island of Koh Tao.

Alexandra Clarke, 26, from Lambeth, south London, was on board for a diving excursion when the blaze occurred. She was in the bathroom at the time the fire started, shortly before a distress signal was sent at 9.25am local time.

There were 21 other people on board, including 15 tourists, two crew members, and four diving instructors and assistants. All of them were evacuated safely by private vessels and volunteers, while a second team fought to extinguish the fire.

The boat was between five and six nautical miles from Koh Tao when the fire ignited in the engine room and quickly spread throughout the vessel, according to Capt Natthaphon Sinpoonphon, the deputy director of the Thai Maritime Enforcement Command Centre of Surat Thani.

Preliminary investigations indicate that the engine room, captain’s cabin, and the rear restroom were damaged by the fire. The exact cause of the fire is still under investigation.

Rescue teams initially had difficulty approaching the boat due to the intense flames and the risk of further explosions caused by fuel on board the vessel.

Capt Sinpoonphon stated, “The search is ongoing for one missing tourist, Alexandra Clarke, from the United Kingdom. Sea conditions are dangerous with strong winds and currents, and all boats in the area have been notified. Search and rescue teams were immediately mobilized.”

The Foreign Office is providing support to the family of the missing British woman and is in contact with local authorities.

A video shared on social media showed the boat engulfed in flames. The Davy Jones Locker was reportedly transporting tourists from Koh Tao to a nearby diving site at South-west Pinnacle.