Officials in Tanzania say at least 31 people have died and more than 100 others are missing after a ferry sank off the coast of Zanzibar.

The vessel went down Wednesday in choppy waters after leaving the commercial capital Dar es Salaam.

A police spokesman said rescuers resumed their search for survivors Thursday, but that bad weather was hampering the effort. Authorities say 145 people have been rescued so far.

More than 200 people died last September when a ferry capsized during a trip around the three islands that make up the Zanzibar archipelago. Prosecutors charged four people with negligence in connection with that accident.