The Russian captain of a cargo ship that collided with a U.S. tanker earlier this week appeared in a U.K. court Saturday where he was remanded in custody over the death of a crew member, who is missing and presumed dead.

The captain of the Solong cargo ship who was arrested after crashing into an oil tanker off the English coast is a Russian national, the vessel’s owner said Wednesday, as maritime experts search for answers.

An oil tanker reportedly on fire in the North Sea after colliding with a cargo vessel. Lifeboats and a coastguard helicopter were called to the collision in the Humber Estuary on Monday morning, believed to involve a US-flagged tanker called the MV Stena Immaculate.