Russian rescuers were searching Thursday for a fishing boat that went missing during a storm in the Sea of Japan with at least 20 crew on board.
The vessel, called Vostok, sent an emergency radio signal while in stormy seas around 200 kilometers off the coast of the far eastern Primorye region Thursday morning local time, according to the Russian emergency services ministry.
"Attempts to communicate with the boat met with no success," the ministry said.
Investigators said the boat had not shown up on global positioning systems after sending the emergency signal.
But a helicopter searching for the vessel spotted a buoy and two life jackets floating in rough seas. Boats and a plane have also been used in the search operation.
Prosecutors said the missing boat has a crew of 20, while the emergency services ministry gave the total number on board as 21. Local media reported one crew member had gone ashore early.
All are Russian, a sea rescue official at the Pacific port of Vladivostok told RIA Novosti.
The boat disappeared in an area of sea around 3 kilometers deep with five-meter-high waves, Russia's fisheries agency said, amid strong winds.
Rescuers have so far covered 4,100 square kilometers of ocean and were set to continue at night using floodlights.
A weather warning was issued Thursday by the regional emergency services ministry, saying boats were at risk of being quickly covered in ice in the Sea of Japan.
"The low temperature and strong wind create such conditions that any ships in the north of the Sea of Japan will accumulate ice. That's what's dangerous," a spokesman for the Primorye region's weather center told RIA Novosti state news agency.
Interfax news agency quoted social media posts from relatives of fishermen in the area saying that weather conditions had caused ice to cover their boats, which affects stability.
The Vostok specialises in catching crab and belongs to a large fishing company based on the Russian island of Sakhalin, Interfax news agency reported.
The boat had been travelling from the port of Donghae in South Korea to Sakhalin.
A probe into possible breaches of safety rules has been opened by Russia's Investigative Committee, which probes serious crimes.
Sakhalin local authorities said the boat was in an area with a lot of shipping and "chances are high for a positive outcome".
In conflicting reports, regional authorities said 13 of the crew are from Sakhalin while the rest are from other Russian regions, Moldova and Azerbaijan.
"We're sure the crew is alive," Russia's emergency services minister Vladimir Puchkov told Interfax.
The ship was in neutral waters at the time it disappeared and was not carrying any catch, Russia's fisheries agency said.
Commercial fishing is a major source of employment in far eastern Russia with high demand for seafood from Asian Pacific countries, but conditions can be harsh.
In 2015, a fishing trawler sank in freezing waters in the Sea of Okhotsk, killing 69 people.
A year earlier, a South Korean trawler sunk in the Bering Sea with 60 people aboard, only seven were rescued.
In 2011, 53 people died when a Russian oil drilling rig capsized and sank off Sakhalin.