The vehicle hit the back side of the faulty truck before another vehicle coming from behind slammed into the vehicle with the six now deceased family members.
Deputy regional police commander Nusu Seleman said at least three vehicles were involved in the crash, leaving seven people dead.
Two of the vehicles are said to be government vehicles with Reg. No STL 6250 Toyota Land Cruiser belonging to the office of the Controller and Auditor General (CAG), another had Reg. No. SU 41173 Toyota Land Cruiser VX from the Public Service Social Security Fund (PSSSF), and a faulted truck with Reg. No. T161 CBB.
He said the six deceased, relatives of Deputy CAG Benjamini Magai were all coming from Geita where they had attended the burial ceremony of a relative.
The deputy RPC named the deceased as Grace Masatu, Godfrey Samson, Andrew Lucas, Luca Magai and Wilhelmina Magai, George Zakayo and Dickson Kitanda (42), the driver of the vehicle. All were residents of Dar es Salaam.
The CAG vehicle was heading to Dar es Salaam while the PSSSF vehicle was heading to Dodoma from Dar es Salaam, he said.
At least three passengers travelling on the vehicle belonging to PSSSF vehicles sustained injuries, who he named as Eliyakunda Mndeme (40) Vick Moshi (41) and Abubakar Mjata(42) who are being treated at the Dodoma referral hospital.
The six bodies were preserved at the Kongwa district hospital while the driver's body was placed at the Dodoma Regional Refugee Hospital.