WELLINGTON, New Zealand — Seventeen fishermen missing for more than 30 hours after their South Korean boat sank near Antarctica were given up for dead Tuesday, with officials saying no one could have survived the icy waters.

New Zealand’s rescue coordination center, which was running a search by private vessels in the remote region, said it had suspended the operation indefinitely.

The No. 1 Insung went down Monday some 1,400 miles south of New Zealand, about halfway to Antarctica. It sank quickly — prompting speculation it struck an iceberg — and the crew of 42 had to abandon ship without donning survival gear.

Nearby ships quickly pulled 20 survivors from the sea, along with the bodies of five dead crewmen, leaving 17 unaccounted for.

Rescue coordination spokesman Dave Wilson said Tuesday it was "exceedingly unlikely" that any of the 17 missing could have survived — with sea temperatures near freezing anyone who fell in would be dead in 10 minutes without special suits or lifejackets.

"Unfortunately the Southern Ocean is an extremely unforgiving environment," Wilson said, using an alternative name for the Antarctic Ocean.

Three South Korean and two New Zealand fishing boats were called into the search by the Rescue Coordination Center on Monday. The New Zealand vessels were released on Monday evening. The three other boats continued to search overnight, but were released on Tuesday.

The search was called off after almost 30 hours because "there was no reasonable expectation that any further survivors would be found," Wilson said in a statement.

Under maritime rules, New Zealand has responsibility for coordinating nearby vessels in its search and rescue region, which covers a wide area of the Antarctic and South Pacific oceans.

It was unclear why the No. 1 Insung sank in light winds and a relatively mild 3-foot  swell.

Wilson said the 20 survivors were onboard the South Korean vessel No. 707 Hongjin and reported to be in a comfortable condition.

South Korea’s Foreign Ministry said on board were eight South Koreans, eight Chinese, 11 Indonesians, 11 Vietnamese, three Filipinos and one Russian.

The confirmed dead included two Indonesians, two South Koreans and one Vietnamese, a ministry official said, speaking on condition of anonymity because of office rules.

The Chinese Embassy in South Korea said four Chinese sailors were missing while four others had been rescued, China’s official Xinhua News Agency reported.

It is the second Korean fishing vessel this year to sink in ocean waters near New Zealand. In August, six men died and 45 were rescued after their boat, Oyang 70, sank in just 15 minutes in calm waters 440 miles east of South Island. A report into the sinking has yet to be released.