A baby drowned and seven people are missing after a boat on which they were having a party sank in Lake Paranoa, the artificial lake surrounding a large part of the Brazilian capital, authorities said Monday.

At least 100 people were on board the boat for a party on Sunday night when the vessel sank for reasons that are being investigated, according to Col. Luis Blumm, head of operations for Brasilia fire rescue.

The only body recovered so far is that of a 6-month-old baby whose mother is one of the seven missing people.

"We still don't have a definitive list of the boat's passengers, and so it's not possible to say how many people were on board," said Blumm, adding that the number of missing people could be greater than seven and that 92 people were pulled out of the water alive.

The search for the missing lasted throughout the night and Monday morning.

Navy officer Fabio Rogerio Leite, the head of the shipwreck investigation, said that the causes of the accident were still not known but there are indications that the boat was overcrowded, given that its capacity was for no more than 90 people.

Investigators are also trying to confirm the stories of passengers who said that the boat sank after being hit by waves from a motorboat that passed quite close by.

The boat began to sink slowly about 8 p.m. on Sunday and passengers were asked to head toward the bow, but in 10 minutes the vessel had gone completely under the water.

Some of the passengers complained that there were not enough life jackets for everyone who was on board the vessel.