Officials in Congo say a freight train has derailed in the country's southeast, killing around 50 people.

A union official, Fernandez Tshibondo, said the train jumped the tracks Tuesday near the station at Katongola, a town in Congo's Katanga province.

Government spokesman Lambert Mende said Wednesday that police had counted around 50 dead, but the toll could go higher. It is common in Congo for people to jump onto freight trains for a free ride.

Agence France Presse reported the death toll was 57.

The train involved was a newly purchased locomotive, AFP reported, which flew off the rails as it went around a bend in a swampy area, causing 15 of its 19 cars to overturn.

Mende said an investigation has been opened into the cause of the crash.