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.

The collision took place about 13 miles (20km) off the East Yorkshire coast, near Hull and Grimsby, in a busy shipping area. The Stena Immaculate was anchored and drifting at a speed of 0.1 knots at 09:48 GMT on Monday, according to ship tracking site MarineTraffic.

The captain of a cargo ship that collided with a U.S. tanker is a Russian national who remains in U.K. police custody, the vessel’s owner said Wednesday, as it emerged that the ship failed several safety checks last year.