SEOUL/WELLINGTON (Reuters) – A South Korean fishing boat sank on Monday in freezing waters near Antarctica and five members of the crew were killed and 17 missing, New Zealand and South Korean authorities said.

Twenty members of the crew of the 614-tonne, 58 meter (190 foot) toothfish boat No 1 InSung had been rescued by a ship.

The boat sank at 6.30 a.m. (12:30 p.m. ET) about 1,850 km (1,150 miles) north of Antarctica and 2,700 km (1,700 miles) south of New Zealand, the country's Rescue Coordination Centre said.

It was not known what caused the ship to sink and no distress call had been made, the center said.

Information from the ship carrying the survivors suggested the boat sank quickly, giving crew no time to put on life jackets or immersion suits, the center said.

The search has been scaled back with three South Korean vessels looking for the missing men. Two New Zealand vessels have stopped searching and an aircraft would not be sent.

"Unfortunately, given the short survival times in water of those temperatures and the length of time it would take for the ... aircraft to reach the search area, it was not a viable option," said New Zealand rescue center controller Dave Wilson.

The water temperature is about 2 Celsius (35 Fahrenheit) which means someone would survive for about 10 minutes without proper equipment, the center said.