A ferry carrying well over its permitted capacity capsized on Lake Kariba in Zimbabwe on Tuesday, killing at least 15 people and leaving 27 others missing. Seventy-seven survivors managed to reach a small island in the lake and are being ferried back to the mainland by rescue boats, while a diving team has been deployed to search for those still unaccounted for.

The vessel, named the Mbuya Nehanda, was designed to carry a maximum of 90 people. Authorities confirmed that ticket records show at least 114 adults were on board, along with five crew members. An unknown number of young children — who do not require tickets — may also have been travelling, meaning the true passenger count could be even higher. The boat was making the roughly five-hour crossing from the town of Kariba to Chalala when it was reportedly struck by strong winds. Local media reported that a warning had been issued the previous day about dangerously high waves on the lake.

Lake Kariba straddles the border between Zimbabwe and Zambia and was formed after the construction of the Kariba Dam on the Zambezi River beginning in 1958. Stretching more than 200 kilometres in length and up to around 40 kilometres wide, it is the largest human-made lake in the world by volume. Rural communities in the region depend heavily on ferry crossings to reach the town of Kariba for goods and services.

Zimbabwean MP Mutsa Murombedzi, who posted video footage of the Mbuya Nehanda departing earlier on the day of the accident, called on authorities to provide accurate information about how many people were on board.