The accident occurred on Lake Mai-Ndombe when the passengers were en route from the town of Kiri to the capital Kinshasa on Thursday evening.
Authorities have not yet given an official death toll. According to the provincial governor, they are waiting for detailed information from rescue workers on the scene.
Similar accidents have become more common in the country as many people abandon road transport for cheaper alternatives by sea. Boats are often overloaded and life jackets and lifeboats may be missing. In addition, many of the transports take place at night, which complicates rescue efforts.
In September, nearly 200 people died when a boat capsized and caught fire.
