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 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.
Four of the survivors, suffering from hypothermia, were airlifted by helicopter to land and taken to hospital after the disaster struck at 12:45 pm (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 death from freezing, according to maritime and rescue websites.
"The Kolskaya keeled to its side ... and sank within 20 minutes. The depth of the water at the site is 1,042 metres (0.65 miles)," Russia's federal water transport agency said in a statement on its website.
Several rescue crafts and helicopters had been sent to the site to scour the waters for survivors from the rig owned by Arktikmorneftegazrazvedka (AMNGR), a unit of state-owned Zarubezhneft. "There is no ecological danger. The vessel was carrying the minimum amount of fuel as it was being tugged by two craft," said a spokesman for AMNGR.
But the incident will deal a blow to efforts by Russia, the world's largest energy producer, to step up offshore oil and gas exploration to stave off a long-term decline in onshore production. The jack-up rig, which has three support legs that can be extended to the ocean floor while its hull floats on the surface, was heading from Kamchatka to Sakhalin when it overturned in stormy winter conditions with a swell of up to 6 metres (19.7 feet).