Officials say at least 163 people were drowned when an overcrowded ferry sank Saturday near Zanzibar, off the coast of Tanzania.

Reports from Zanzibar suggest the ferry, the MV Spice Islander, was even more overloaded than previously thought, with roughly 750 people on board.

The latest casualty report from authorities in Stone Town, Zanzibar's capital and main port, says there are 579 known survivors of the ferry disaster, some of whom are badly injured.

Large crowds gathered at the site where bodies are being taken and counted, hoping to get word about friends or relatives who were on board.

The ferry sank early Saturday during a trip around the three islands that make up Tanzania's Zanzibar archipelago.

Emergency crews and vessels in the area have been searching the waters where the ferry went down.

There is no clear information yet about how many people were aboard the ill-fated ferry, or its operating condition.