Police have been questioning the captain of a cargo vessel after it crashed into a North Sea gas platform 40 miles (64km) off the Norfolk coast.
The Jork struck the unmanned Viking Echo platform just before 1800 BST on Saturday.
Coastguards said a 56-year-old Polish man had been arrested in connection with the incident.
The 2000-tonne vessel, which had been carrying grain from Germany sunk in deep water at about 0800 BST on Sunday.
Mario Siano, watch manager at Yarmouth Coastguard, said: "The captain of the ship is in police custody and the rest of the Polish crew are being housed in a local hotel."
It is believed that Norfolk Police were seeking a Polish interpreter before starting the interview with the captain.
Mr Siano added: "It's a freak accident and we don't know what caused it."
Mr Siano said the vessel sunk after bursting its hull, caused by the wheat on board "swelling".
The coastguard was called after reports the Jork was listing heavily and six crew members wearing lifejackets had to be rescued from the sea.
The captain remained on board to try to save the ship, which was destined for the River Humber, but also had to be rescued.
Two coastguard boats and a RAF rescue helicopter, from Wattisham Airfield, Suffolk, attended the incident.
A spokesman for gas suppliers ConocoPhillips said only "very slight" damage had been caused to its platform.
The Marine Accident Investigation Branch is looking into the cause of the crash.