The regional governor, Paul Makonda, said: "Initial information indicates he was kidnapped by whites travelling in two vehicles".
Mr Dewji, who is a fitness enthusiast, was kidnapped by four masked men outside a swanky hotel gym in an affluent neighbourhood of Tanzania's commercial capital, where he was going for his routine morning workout.
"Also in the report, the Dar es Salaam police chief, Lazaro Mambosasa, at a press conferences said the kidnappers had "shot into the air" before bundling Mr Dewji into a vehicle".
The armed men were foreigners, the Swahili Times reported on Twitter, citing Police Commander Lazaro Mambosasa.
Police have thrown a security cordon around the country as the hunt for abducted Tanzanian billionaire Mohammed Dewji got underway. "I personally saw the person to be Mo Dewji". He served as an MP from 2005 to 2015.
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It is believed that the abductors had access to guarded hotel grounds because its gates were "believed to have been left open deliberately", suggesting that they may have had help from hotel staff. Mambosasa also revealed that several suspects, including hotel staff, were interviewed and multiple arrests have already been made.
They then sped off while shooting in the air.
His current net worth is about US$1.5 billion, according to the Forbes Billionaires list.
Mohammed Dewji, a Tanzanian business tycoon said to be Africa's youngest billionaire, photographed during an interview at his office in Dar es Salaam, Tanzania, April 23, 2015.
Three women are among the 55 richest people in Africa, according to Ventures magazine.