A vessel with a storage capacity of two million barrels of oil has exploded off the coast of southern Nigeria’s Delta state, raising fears of an environmental disaster and concerns about the fate of its crew.

Shebah Exploration & Production Company Ltd (SEPCOL) said on Thursday that flames had engulfed the Trinity Spirit following the blast a day earlier.

The floating production, storage and offloading vessel can process up to 22,000 barrels of oil a day, according to the operator’s website.

Images published by local media showed thick black smoke billowing from a sinking ship engulfed by flames.

The vessel was located at the Ukpokiti Terminal, along the coast of the oil-rich Niger Delta region.

Joe Sunday, an assistant boat driver, said he was in one of the two speedboats out at sea on Wednesday morning to pick some crew who were due to take time off from work but could not reach the vessel because it was consumed by fire.

“We drove round to see if we could see people but we did not see anybody and the fire was still blazing,” Sunday told Reuters news agency at a port in Warri.

Tiby Tea, chairman of Maritime Union for Nigerian Ports Authority in Warri, confirmed that two boats sent out to the vessel could not find anyone.

“At this time there are no reported fatalities but we can confirm that there were 10 crewmen on board the vessel prior to the incident,” SEPCOL Chief Executive Ikemefuna Okafor said in a statement.

An investigation was under way to determine the cause of the accident, he said, adding that the company was working to “contain the situation”.

Nigeria’s regulatory agency for upstream operations, NUPRC, said the explosion had led to a “major fire” and that it had “commenced investigations into the incident”.

“The commission will take necessary measures to ensure that all safety and environmental measures … to safeguard lives and the environment are put in place,” spokesman Paul Osu said.