Dozens were killed early Thursday morning when a Russian fishing trawler sank in the Sea of Okhotsk.

Officials said that at least 56 people are dead, 63 people were rescued, and the fate of 13 others was unknown. 

Investigators are still trying to determine the cause of the sinking, but said the vessel may have struck drifting ice off the Kamchatka Peninsula. Vasily Sokolov, deputy chief of the Russian Fisheries Agency, denied that the vessel was overloaded, according to Russia's Interfax news agency. 

The report contradicted a statement by the acting governor of Sakhalin island, Oleg Kozhemyako.

"Given the fact that the tragedy occurred quickly and unexpectedly, and the ship was registered and met all technical requirements, I think there was a violation of rules when it comes to overload and balancing of the vessel," he told LifeNews television. 

No distress call was sent before the sinking around 4am local time. 

More than 26 fishing boats and 1,300 people were nearby and assisted with the rescue efforts. At least one body was found in a life boat 65 miles away from the sunken ship on Thursday evening. 

Viktor Klepikov, coordinating captain of the Petropavlovsk-Kamchatsky maritime rescue coordination centre, told Reuters that the water was near freezing at the time of the sinking. 

Rescued crew members were transported to Magadan by Mi-8 helicopters dispatched by the Russian Emergencies Ministry. The agency also set up a telephone hotline for families of the crew, and posted updates on the rescue on their website. President Vladimir Putin sent his condolences and mobilised efforts to help the survivors. 

Of the 132 crew on board, 78 were from Russia, 42 from Myanmar and the remaining were from Latvia, Ukraine and Vanuatu.