At least two people have died and more than 50 are missing after an oil drilling rig sank in freezing seas in the Russian far east.
The Kolskaya rig was being towed some 200km (125 miles) off Sakhalin island when it capsized in a fierce storm.
Fourteen people have been rescued but it is feared the rig overturned before the rest of the 67 people on board could escape on to life rafts.
Rescue efforts have been hampered by poor weather conditions.
Helicopters and a plane helped scour the area amid high winds and waves of up to 12ft (4m) but the search was halted as night fell.
Empty life rafts
"According to reports from the scene of the rescue operation, the Kolskaya platform has sunk completely," the regional head of the emergencies ministry, Taimuraz Kasayev, told a news briefing.
The accident in temperatures of -17C at around 14:00 local time (0200 GMT) in the Sea of Okhotsk happened as the rig was being towed from the eastern peninsula of Kamchatka to Sakhalin.
An unnamed regional emergencies ministry spokesman told the AFP news agency that the portholes of the rig had been "damaged by ice and waves, and water began going into the vessel".
He said the crew had been waiting to be evacuated by helicopter but the platform capsized and sank before they could get to their rescue rafts.
Two out of the four life rafts were reportedly found with nobody on board.
The spokesman confirmed to AFP that 14 people had been rescued but were in a serious condition, and two bodies "without signs of life" had been spotted by rescue workers who are "trying to pull them out".
An investigation has been launched to decide whether any safety regulations were violated transporting the Kolskaya in bad weather.
The rig, operated by Russian exploration firm Arktikmorneftegazrazvedka, was not involved in any drilling work at the time, and there is no danger of any oil spill, Russian officials said.