The ferry MV Nyerere capsized on Thursday afternoon just a few meters 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.
Thirty-seven people had been rescued from the sea, Jonathan Shana, the regional police commander for the port of Mwanza on the south coast of the lake told Reuters by phone on Friday.
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 Tanzania’s Indian Ocean archipelago of Zanzibar.