* Death toll rises to 80, around 150 said on board

* 36 rescued, but boat gone missing

* Authorities seek U.N. help to transport survivors

(Updates death toll, adds quotes, background)

By Christo Johnson

FREETOWN, Sept 9 (Reuters) - A boat carrying children in Sierra Leone back from their school holidays capsized in a heavy storm off the capital Freetown, killing at least 80 of its 150 passengers, police said on Wednesday.

Emergency services rescued 36 people and were continuing the search for more survivors from the wreck on Tuesday, federal police spokesman Ibrahim Samuro told reporters.

"The rest are still missing. The vessel cannot be traced," Samuro said of the search effort off the coast by Freetown's Tombo suburb.

"Most of the dead were children between the ages of eight and 16 years old," Sam Bangura, a senior police officer, told Reuters earlier, adding that the boat capsized when it drifted into a heavy storm and its engine failed.

Abu Essay, one of the survivors, said most of the victims were children returning from the town of Waterloo, 12 km (7.5 miles) away from Freetown, where they had spent their holidays.

Lack of maintenance and over-crowding mean such accidents are frequent in West Africa, which is currently being battered by seasonal storms and heavy rain that on land have already killed more than 160 people and displaced thousands more.

"The last time we had such high numbers in a boat accident was during the war when people were trying to escape from Sierra Leone to take refuge in neighbouring countries," said Mary Mye-Kamara at the Sierra Leone Office for National Security, of a decade of deadly civil war which ended in 2002.

"What we are trying to do is to fly the survivors to Freetown because adequate health facilities are lacking in the area of the incident. We trying to see if the U.N can assist in transporting them over to Freetown," she said by telephone.

Mye-Kamara decline to comment on whether over-loading had been a factor, adding: "That is all speculation for now, investigations are still continuing." (Additional reporting by George Fominyen in Dakar; writing by David Lewis and Mark John; editing by Philippa Fletcher)

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