The aircraft, which departed from the commercial capital Dar es Salaam "fell in Lake Victoria this morning due to storms and heavy rains"
A commercial flight operated by Precision Air on Sunday crashed into Africa's largest lake near Bukoba airport Tanzania.
The passenger plane crashed while attempting to land in stormy weather at the airport, according to the airline.
Fifteen people are said to have been rescued so far but it was not known how many passengers were on board the Precision Air flight or whether there were any fatalities, Tanzania Broadcasting Corporation (TBC) reported.
The aircraft, which departed from the commercial capital Dar es Salaam "fell in Lake Victoria this morning due to storms and heavy rains", TBC reported.
Tanzania's President took to social media to call for calm while rescuers worked at the site of a downed plane.
"I have received with sadness the information of the crash of the Precision Air flight at Lake Victoria, in the Kagera region," President Samoa Suluhu wrote on Twitter Sunday.
"I send my condolences to all those affected by this incident. Let's continue to be calm as the rescue operation continues and we pray to God to help us."
Video footage and images that circulated on social media showed the plane almost fully submerged, with only its green and brown-coloured tail visible above the water line of Lake Victoria, Africa's largest lake.
Rescue boats were deployed and emergency workers were continuing to rescue other passengers trapped in the plane, TBC added.
Precision Air, Tanzania's largest privately owned airline, identified the plane as flight PW 494 and said it was "involved in an accident as it was approaching Bukoba Airport". The airline's statement gave no further details.