BANGKOK - Authorities in Thailand on Thursday were working to avert a leak from a storage vessel carrying 400,000 barrels of crude oil.

One crew member was killed after seawater entered the hull of The Benchamas 2 when a seal malfunctioned during maintenance earlier this week.

Navy spokesperson Admiral Prokgrong Monthatphalin said multiple agencies were working to recover the body of the dead crewman, fix the leak and avert an oil spill.

"The vessel's condition is safe and weather conditions are not interfering with the rescue operations. However, there is no electricity in the engine room ... it is affecting assessment of the situation," he said in a statement.

Operated by a unit of Chevron, the 25-year-old vessel has a storage capacity of 650,000 barrels and operates at the Benchamas field in Block B8/32 in the Gulf of Thailand.

It is located about 207 km (129 miles) off Sattahip in Chon Buri province, where Thailand has its biggest navy base.

Chevron in a statement expressed sadness at the death of the crew member, a contractor, and said all non-essential personnel were being removed from the vessel.

"The safety of all personnel and the protection of the environment remain our top priorities. We have engaged and notified the relevant authorities and are working with all stakeholders," it said.

A spill from an undersea pipeline operated by Star Petroleum Refining Pcl in the same region in January 2022 leaked an estimated 50,000 litres (13,209 gallons) of oil.

The spill occurred just 20 km (12 miles) off the coast of Rayong province and the slick reached local beaches.

(Reporting by Chayut Setboonsarng; writing by Martin Petty; editing by Jason Neely)