Rescuers in Tanzania have retrieved at least 136 bodies a day after a ferry sank on Lake Victoria, the top police official said, but scores more are missing.

The ferry MV Nyerere capsized just a few metres from the dock on Ukerewe, the lake’s biggest island, which is part of Tanzania. Initial estimates suggested that the ferry was carrying more than 300 people.

In an address to the nation, President John Magufuli declared four days of mourning and warned against politicizing the disaster.

“Let’s leave designated authorities to investigate,” he said. Some opposition politicians say the government responded late to the sinking.

State-owned Taifa Leo reported on its website on Friday that top officials of the Surface and Marine Transport Regulatory Authority (Sumatra) would be questioned in regard to the accident. Preliminary investigations, the paper said, showed the ferry had carried more passengers than its capacity permitted.

Thirty-seven people had been rescued from the lake, Jonathan Shana, the regional police commander for the port of Mwanza on the south coast of the lake told Reuters.

Shana said more rescuers had joined the operation when it resumed at daylight on Friday. He did not give exact numbers.

The precise number of those aboard the ferry when it capsized was hard to establish since crew and equipment had been lost, officials said on Thursday.

Tanzania has been hit by several major ferry disasters over the years. At least 500 people were killed when a ferry capsized in Lake Victoria in 1996. In 2012, 145 people died when a ferry sank off the shore of the archipelago of Zanzibar.