Brazilian authorities pulled 11 more bodies out of the Amazon's Solimoes river on Wednesday where an overcrowded boat capsized at the weekend, and updated the death toll from the disaster to 45.

Emergency services had previously put the toll from Sunday's tragedy at 29, while dozens of others were still reported missing.

Around 110 people were believed to be aboard the Comandante Sales boat when it sank near Manacapuru, about 80 kilometres from Manaus, the capital of Amazonas state.

Authorities rescued 70 people, and have not ruled out the possibility that other passengers survived and returned home without alerting anyone.

The navy said the boat was not authorised to operate, and police said it was overcrowded. Many of the passengers were young people returning from a party.

Strong whirlpools apparently caused the boat to capsize at a spot where the river was 100 meters deep, while strong currents dragged it for 20 kilometres.

AFP