Satellite imagery shows a slick of oil stretching from the site of an FPSO explosion that has killed at least three crew members off Nigeria.

The image from the European Space Agency’s Copernicus Sentinel-2 mission shows an oil slick extending at least 20 km, according to Antoine Halff, chief analyst at satellite data analytics company Kayrros.

He said on Twitter that imagery from Earth observation company Capella Space also shows the slick.

Meanwhile, Nigeria’s Shebah Exploration & Production Co Ltd said three crew members were found dead and three were found alive after the incident involving its 22,000-bpd floating production, storage and offloading vessel Trinity Spirit (built 1976).

That leaves the four remaining crew members still missing.

“Our priority remains focussed towards establishing the whereabouts, safety, and security of the four crew members still missing,” the company said, according to Reuters.

The incident, which took place 2 February when the vessel suffered an explosion and fire, is also believed to have led to the spilling of 50,000 barrels of oil, according to Upstream. Trinity Spirit was serving the Ukpokiti oil field off Nigeria’s Delta state.

Bashir Jamoh, director-general and chief executive officer of the Nigerian Maritime Administration and Safety Agency, said on Friday that a joint investigation team of several agencies was dispatched to Ukpokiti to carry out a preliminary assessment of the incident.

Then on Monday, Nigerian environment minister Sharon Ikeazor said the fire was totally extinguished.

She said the National Oil Spill Detection Response Agency was scheduled to carry out its second day of overflights, according to local news media.

She downplayed the potential for a major oil spill.

“While the cause of the fire incident is yet to be fully determined, the environment around the FPSO is only slightly covered by sheen and emulsified oil,” Ikeazor said, according to Abuja newspaper Leadership.

Some 50,000 to 60,000 barrels were believed to be on board the FPSO at the time of the incident.

Photos of the Trinity Spirit after the blast showed the vessel was partially submerged and broken in two.