A drilling rig with 67 crew on board capsized and sank off Russia’s far eastern island of Sakhalin on Sunday while being towed through a winter storm, leaving more than 50 dead or missing in the icy Sea of Okhotsk.

Emergency officials said the crew of an icebreaker and tugboat rescued 14 workers alive from the jack-up rig, the ‘Kolskaya’, which was operated by a Russian offshore exploration firm. They recovered four bodies from the water.

“The Kolskaya keeled to its side … and sank within 20 minutes. The depth of the water at the site is 1,042 metres (3,400 feet),” Russia’s federal water transport agency said on its website.

Four of the survivors, suffering from hypothermia, were airlifted by helicopter to land and taken to hospital after the disaster struck at 12:45 p.m. (0145 GMT).

The rest of the crew were missing, 200 km (125 miles) off the coast of remote Sakhalin island. The water temperature was one degree Celsius (33.8 Fahrenheit), giving survivors around 30 minutes before freezing to death, according to maritime and rescue websites.