A passenger boat carrying 70 people sank in Brazil’s Xingu river in the Amazon region on Monday, killing at least 10, AP reported on Wednesday. While 15 people have been rescued, several others are still missing. The mishap is believed to have taken place on Tuesday night.

The vessel was travelling from Santsarem to Vitoria do Xingu when it sank in the Xingu river in the state of Para, BBC reported. The boat was being used to illegally ferry passengers through the waterway, according to Brazilian newspaper Folha de S. Paulo.

Brazil’s State Agency for Regulation and Control of Public Services said the vessel was not registered with it, and hence, it was not authorised to ferry passengers. Rescue operations are under way. The police are investigating the cause behind the accident.