Abducted Tanzanian tycoon Mohammed Dewji's family on Monday announced a Tsh1 billion (Sh44 million) reward for anyone with information on his whereabouts.
Mr Dewji, who is known as Mo and has a personal fortune estimated at $1.5 billion, was seized by four armed men on Thursday as he arrived for his daily dawn workout at a hotel in Dar es Salaam.
"The family would also like to assure any person (s) giving information that all of this will remain strictly confidential and shall stay exclusively between person (s) and the family", according to family spokesman Azim Dewji.
'The family is offering a reward of a billion shillings to any person who has information leading to the whereabouts of our son, ' family spokesman Azim Dewji told a press conference.
30 people have already been arrested in connection to the kidnapping and are assisting Tanzanian police with the investigations.
Police said he had no security detail with him when he was abducted.
Officials have implicated the involvement of foreigners, saying he was taken by "whites".
Dewji was chief executive of the MeTL Group which operates in some 10 countries and has interests in agriculture, insurance, transport, logistics and the food industry.
He was a member of parliament from 2005 to 2015, and in 2013 he became the first Tanzanian to feature on the cover of Forbes magazine.
Dewji was also the main shareholder in Tanzania's Simba FC football club.