MOSCOW (AP) — A Russian freezer trawler with an international crew of 132 sank Thursday morning in the Sea of Okhotsk off of the Kamchatka Peninsula and at least 54 crew members were killed, rescue workers said.

Emergency services in Kamchatka, citing the head of the rescue operation, said 63 crew members were rescued and the fate of the remaining 15 from the Dalny Vostok trawler was unknown.

More than 25 fishing boats in the area helped to rescue the crew members, emergency services said in a statement on their website.

No cause for the sinking was given, but the Interfax news agency said drifting ice in the chilly Pacific waters may have played a role.

Rescue workers were able to lift aboard fishing boats 63 crew members and 54 bodies, the news agency said.

The trawler sent no distress signals prior to sinking, Interfax said.

The Russian Emergencies Ministry sent an Mi-8 helicopter with rescuers and doctors aboard to deliver medical assistance and transport rescued crew members to hospitals in the city of Magadan, the ministry said on its website. It also set up a telephone hotline for families of the crew, the ministry said.

Among the 132 crew members, 78 are from Russia, 42 from Myanmar and the rest from Latvia, Ukraine and Vanuatu.

The search and rescue operation involved 1,300 people and 29 units of equipment, emergency services said.