An oil storage vessel that exploded off the coast of Nigeria this week was holding around 50,000 to 60,000 barrels of crude oil at the time of the incident, Minister of Environment Sharon Ikeazor said on Saturday.

Nigeria's Shebah Exploration & Production Company Ltd (SEPCOL) said on Thursday that flames had engulfed the Trinity Spirit floating production, storage and offloading (FPSO) vessel following a blast a day earlier.

Ikeazor said the National Oil Spill Detection and Response Agency has called the oil industry operators and the Clean Nigeria Associates, a co-operative responding to oil spill incidents for support.

SEPCOL, in receivership, said it was working with authorities to inspect the vessel after the fire burnt out and an investigation team has been launched to establish the cause of the explosion.

It reported no casualties and is investigating the whereabouts and safety of 10 crew members who were on board the vessel prior to the incident, SEPCOL said in a statement.

An industry source with knowledge of operations of the Trinity Spirit FPSO said until five years ago other companies, including large oil traders, stored their crude on the vessel, which had capacity to produce 22,000 barrels per day and could store 2 million barrels.

The Trinity Spirit is the primary production facility for OML 108, which covers 750 square km (290 square miles) of water off the Niger Delta, ranging from a depth of 30 metres to 213 metres, SEPCOL's website said.

(Reporting by Camillus Eboh; Writing by Chijioke Ohuocha; Editing by Alex Richardson)