A serious fire onboard the ultra-large containership Maersk Honam in the Arabian Sea has left four seafarers missing.

Maersk Line said the 2017-built, 15,262 teu Maersk Honam headed from Singapore to Suez reported a serious fire in the vessel’s hold at 15-20 hrs GMT on Tuesday.

The crew sent out a distress call after firefighting efforts onboard were unsuccessful and 23 out of 27 crew were successfully evacuated to the vessel ALS Ceres, which arrived on the scene at around 1830 hrs GMT. An explosion was reported to have followed the initial fire with flames rising up 25 m from the main deck of the vessel to the bridge.

Maersk said that search and rescue operations were ongoing for four crew members missing in the fire. The Singapore-flagged vessel is currently 900 nm Southeast of Salalah Oman and the situation was described as “very critical” by Maersk. Two of the rescued crew members are receiving medical attention on the ALS Ceres.

“We’ve received the news of Maersk Honam and the four missing crew members with the deepest regret and are now doing our outmost to continue the ongoing search and rescue operations. This by rerouting our own vessels, with assistance of vessels in the area – most notably ALS Ceres that thankfully acted promptly upon our distress call – and the local authorities,” said Søren Toft, coo and member of the Executive Board, AP Moller – Maersk.

Toft said the rescued seafarers were obviously distressed and the company was is the process of informing relatives of all crew members. “We will offer crisis counselling for the seafarers signing-off and returning to their families and our thoughts and deepest empathy go out to the families of the crew members that are still unaccounted for. We will offer them all the support we can in this very difficult situation,” he said.

The nationalities of the 27 crew members are: India (13), the Phillipines (9), Romania (1), South Africa (1), Thailand (2) and the United Kingdom (1).

The containerships MSC Lauren, Edith Maersk and Gerd Maersk, all sailing the Arabian Sea, were expected to early morning local time on Wednesday.

The Maersk Honam is carrying 7,860 containers. Container fires can be extremely difficult to bring under control reaching temperatures of over 500 degrees centigrade and spreading quickly to other containers and burning for weeks on end.