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.

British authorities have arrested the captain of a cargo ship as they investigate the cause of a fatal crash between the vessel and an oil tanker shipping jet fuel for the U.S. military in the North Sea.

A port official said he was told the North Sea collision produced "a massive fireball" and the cargo ship's owner said one crew member was missing.