About 15 people had been found alive as of Wednesday morning, but dozens are still missing, according to a.
That boat had 133 people on board, of which at least 21 had been rescued, naval commander Flavio Almeida told AFP.
At least three people died Thursday when a Brazilian ferry with capacity for 100 passengers capsized, local media reports said just a day after another ferry sank, killing at least 10.
The vessel was running the short route from the island of Itaparica across the bay to the city of Salvador, capital of Bahia state, when it went down.
Boat travel in northern Brazil is a common mode of transportation considering the small number of major roads in the Amazon region.
As of Wednesday evening, only 19 people had been rescued.
The authorities count 23 survivors and the search continues to try to save the seven people still missing. It is also reported that the ship has made a night flight from Santarem to Vitoria do Xingu.