About 50 people have died after a boat capsized on a river in the Democratic Republic of Congo, officials say. The vice-governor of Tshuapa province in the north of the country said the cause of the accident was not clear. He said another 50 people had survived when the boat tipped over as it was travelling from Monkoto to Mbandaka. River transport is common in DR Congo as there are few roads or railways, but vessels are often overloaded and accidents are frequent. Tshuapa Vice-Governor Richard Mboyo Iluka told the AFP news agency that the boat had been travelling at night, which is illegal, and did not have lights. Last month more than 40 people drowned when travelling to neighbouring Congo-Brazzaville.