By Thomas Escritt and Anthony Deutsch

AMSTERDAM (Reuters) - Human error was probably to blame for a collision that killed five crew and sank the Baltic Ace car carrier, its Greek manager said on Thursday, as the Dutch rescuers searched icy North Sea waters for survivors.

The Dutch Defence Ministry said conditions were treacherous when the Corvus J container ship and the Baltic Ace collided, sending 1,400 new cars, mostly Mitsubishis from Japan and Thailand, to the seabed on Wednesday evening.

But Panagiootis Kakoliris, operations manager at Stamco Ship Management Co., Ltd. which managed the Baltic Ace, told Reuters that sea conditions were normal when the 23,500-tonne ship was lost. Six sailors remain missing.

"You cannot control some things. This happened in good weather, normal weather. There was good visibility, so I feel most probably there was a human error," said Kakoliris.

He did not say where the thought the blame might lie.

The Polish captain was being treated in hospital and it was not known if he had spoken to the authorities about what had caused the collision with the Corvus J, some 50 nautical miles from Rotterdam port.

The car carrier sank in 15 minutes and the wreck is now completely submerged.

The Dutch coastguard said freezing cold and gale force winds meant there was only a slim chance of finding the Baltic Ace's missing crew. The sailors on the Baltic Ace were from Ukraine, Bulgaria, the Philippines and Poland. The nationalities of the dead and missing were unknown.

HUNT FOR SURVIVORS

The coastguard said 13 people were rescued on Wednesday night but snow and three-meter-high waves were adding to difficulties of finding more crew.

Eleven of the Baltic Ace's 24 crew managed to scramble into four life rafts before the ship went down and were winched to safety by helicopters. Others were picked up by the Corvus J.

The bodies of five sailors were recovered, the Dutch coastguard said. Two of the dead sailors were found in survival suits designed to protect their wearers fully from the elements.

Peter Westenberg, spokesman for the Dutch coastguard, said six crew were still missing. "We are not expecting any survivors," he added. "Some of the victims could still be in the ship, but the weather is not good to send divers down."

Karen Gelijns, a spokeswoman for the Dutch defence ministry, said: "It was a wild night, there were force 6 winds, very rough seas, and it was snowing."

Two Dutch naval patrol ships, the Friesland and the Groningen, stayed at the site of the wreck when the search was called off for the night until the Dutch coastguard resumed control of the operation in the morning.

"The captain of the Friesland, who commanded the operation, said they knew the window of opportunity was small. The Baltic Ace sank in 15 minutes," Gelijns said, "so they knew nobody would have had time to put on protective clothing. But they did all they could."

(Additional reporting by Sara Webb, Gilbert Kreijger, and Ivana Sekularac; Editing by Ruth Pitchford)