A boat ferrying at least 80 people home from a party sank in Brazil's Amazon region early Sunday, killing at least 15 and leaving dozens missing, according to rescue officials and Brazil's government.
The wooden Comandante Sales ferryboat capsized in a pre-dawn rainstorm on the Solimoes River, one of the Amazon's largest tributaries, said Fire Lt. Col. Raimundo Rodrigues da Silva.
It was unclear how many passengers the Comandante Sales was authorized to carry, but authorities said the ferry had been grounded several months ago after failing an inspection. Boats serve as buses in the area because there are few roads.
Rescue workers had recovered the bodies of 15 people by Sunday evening when the search was called off for the night, according to Agencia Brasil, the government's official news agency. Most of those who died were women and several dozen other people were unaccounted for, Silva said.
The search was scheduled to resume Monday, and an investigation into the cause of the accident is expected to take at least three months. Navy Lt. Raimundo Lenilton de Araujo told Agencia Brasil that torrential rains may have been a factor.
Amazon boats are frequently overloaded with passengers and cargo, which also may have been a factor, Silva said.
Revelers had rented the boat to travel from their small river town to another for a party, Brazilian media reported.
Some survivors swam to shore while others were rescued by other boats in the area, local media reported -- although authorities did not know how many survived. Silva said the boat may not have had a passenger list.
Brazil's navy joined about 45 rescue workers, including 15 divers, in searching the area about 70 kilometers (44 miles) from Manaus, the capital of Amazonas state.
The Navy issued a statement saying the boat had been ordered not to travel following an inspection in January because it lacked the proper paperwork and a qualified crew, Agencia Brasil reported. Calls to the Navy's Amazon headquarters went unanswered.
Boating accidents have killed more than two dozen people in Brazil since February, when a two-story wooden ferry carrying more than 100 people collided with a barge loaded with fuel tanks on the Amazon River, killing 16.
In March, a similar boat carrying 12 tourists and a crew of 10 on a wetlands fishing trip sank in the Pantanal area in Mato Grosso state south of the Amazon, killing nine.