Officials say the number is likely to rise further as search and rescue operations continue after the disaster on Thursday afternoon.
At least 37 people were rescued from the sunken ferry as of Thursday evening, when rescue teams called off their mission overnight.
It is not clear how many people were on board, though such ferries often carry hundreds of people and are overcrowded.
Accidents are often reported on the large freshwater lake, which is surrounded by Tanzania, Kenya and Uganda.
Some of the deadliest have occurred in Tanzania, where passenger boats are often said to be old and in poor condition.
In 1996, more than 800 people died when the passenger and cargo ferry MV Bukoba sank on Lake Victoria.
Nearly 200 people died in 2011 when the MV Spice Islander I sank off Tanzania’s Indian Ocean coast near Zanzibar.