Seventy-six people survived after the vessel went down but dozens are feared drowned in the Congo river.
Thirty-six people were missing and feared drowned after a boat sank in the Congo river on the outskirts of Kinshasa.
The vessel, which was travelling to the Democratic Republic of the Congo's capital, went down overnight on Sunday in Maluku commune, about 100km (62 miles) from the centre of the city.
Seventy-six people survived, police wrote on Twitter.
"The cause of the accident is not yet known," police spokesman Colonel Pierrot-Rombaut Mwanamputu told AFP news agency.
Lake and river transport is widely used in the Republic of Congo as the highway system is poor, but accidents are common, often caused by overloading and the unsafe state of vessels.
The boat involved was called a "baleiniere" or "whaler" - a commonly used flat-bottomed vessel between 15 to 30 metres (50 to 100 feet) long by two to six metres wide.
In the vast majority of accidents, passengers are not equipped with life jackets and many cannot swim.
Al Jazeera