South Korean officials expressed fear on Tuesday of a huge death toll after rescuers failed to find any of the more than 50 fishermen missing after their ship sank amid high waves in the freezing waters of the western Bering Sea on Monday.

Authorities rescued seven crew members and recovered one body, but weather and water conditions complicated the search for the others, an official from the South Korean fisheries and oceans ministry said on condition of anonymity because of office rules.

The crew included 35 Indonesians, 13 Filipinos, 11 South Koreans and one Russian inspector, the official said. Russian authorities said there were 62 people aboard the ship, which sank near Russia.

The South Korean ministry official said it's believed that the ship, which was catching pollock, began to list after stormy weather caused seawater to flood its storage areas. Kim Kang-ho from Sajo Industries, the canned tuna company that owns the ship, said the 2,000-ton vessel was 36 years old.

An official from South Korea's foreign ministry, who refused to be named, citing office rules, said Tuesday morning that the death toll was expected to rise because rescuers failed to find any of the missing passengers.

Four fishing ships that were operating nearby continue to search for survivors, but harsh weather conditions have limited their mobility, the official said.

South Korean Prime Minister Chung Hong-won said at a Cabinet meeting that the government will work with Russia to speed up the rescue efforts.