NAIROBI, Kenya — The death toll from the capsizing of a Tanzanian ferry on Lake Victoria had climbed to at least 131 people and could rise further, officials said on Friday as they vowed to investigate the disaster.

Exactly how many people were onboard the ferry, the MV Nyerere, remains unclear, as the authorities fear that the person who had handled ticketing was among those who drowned. But some estimates put the number of passengers on the boat when it overturned on Thursday at more than 300, according to Reuters.

Officials say the ferry appears to have been overloaded, with far more passengers than was advisable. One local official said the ferry’s capacity was 100 passengers.

By Friday evening, dozens of survivors and 131 bodies had been pulled from the water, and identification of the victims was underway, said Isack Kamwelwe, Tanzania’s minister for communication, transport and infrastructure. The numbers mounted steadily as the day went on, and officials cautioned that the death toll could continue to rise.