Brazil ? A boat with 110 people aboard sank in the Brazilian Amazon on Sunday, killing at least 12 people and leaving dozens missing, authorities said.

The Comandante Sales capsized before sinking swiftly on the Solimoes River, one of the largest branches of the Amazon, Fire Lt. Col. Raimundo Rodrigues da Silva said. The vessel was carrying passengers who were returning from a party near the jungle city of Manaus, he said.

The bodies of 10 women and two men were recovered and several dozen people were unaccounted for, Silva said. The victims had not been identified and it is unlikely the boat kept a passenger list, he said.

It was not clear what kind of boat the Comandante Sales was or how many passengers it was equipped to carry. It is possible the vessel was overloaded, but the cause of the sinking was still being investigated, Silva said. He added that passengers may have been trapped inside the boat because many were sleeping when it went down.