A bus packed with people heading home for the holidays plunged into a river in South Africa's central Free State province Saturday, killing 20 people and injuring 77, police said. The bus, which was traveling from Mpumalanga province in the north to the Eastern Cape in the south, was on a dirt road near the town of Wepener, about 500 kilometers (300 miles) south of Johannesburg. As it reached a junction with a tarred road, the driver apparently lost control and the bus careered off a bridge into the river below, police spokeswoman Capt. Elsa Gerber said. The dead included six children, she said. The injured were rushed to hospital. It was not immediately clear how many passengers were on board, but a search by police divers uncovered no additional victims, Gerber said. Police were investigating the cause of the accident. This is one of the busiest times on South African roads and accidents are common.