REUTERS, Brasilia - A boat carrying around 110 people, more than twice its capacity, sank on Sunday at dawn on a major river in the Amazon rain forest, rescue workers said.

The boat sank before 6 a.m. on the Solimoes River, about 50 miles from Manaus, a spokesman for the fire department in the town of Manacapuru told Reuters.

It was returning an estimated 110 revelers from a party in the interior of the state, he said. Fifteen bodies were found and an unknown number was still missing, Coronel Antonio Dias, commander of the Amazonas fire brigade, told Reuters by telephone from Manaus.

According to CBN radio, as many as 150 people were on board the boat, which had a capacity of 50 people. Forty-three fire fighters, including 16 divers, were participating in the rescue operation, which could take several days in the silty river, Dias said.

Boats traveling on the many rivers in the Amazon region are frequently loaded beyond capacity and are seldom controlled by authorities.

"There are thousands of these boats in the region and strong currents in the rivers, so these accidents happen," said Dias.