Officials have said people were trying to siphon fuel from the vehicle on a main road in the Morogoro region when it exploded, killing 71.
Ahead of the funeral, hundreds of relatives visited the hospital to try to identify their dead family members, but many were burnt beyond recognition.
As a result, officials have promised to do DNA tests.
This is the latest in a series of similar disasters across Africa, and Tanzania’s President John Magufuli has pleaded people to stop risking their lives by siphoning fuel from broken-down tankers.
“There are vehicles that carry dangerous fuel oil, as in this case in Morogoro, there are others that carry toxic chemicals or explosives, let’s stop this practice, please,” AFP news agency quotes him as saying on Saturday.
Magufuli declared three days of mourning.
The incident occurred in Morogoro region, about 200 km (124 miles) west of the port city of Dar es Salaam, the country’s commercial capital.
The city of Morogoro is on a major route for transporting cargo and fuel from the port.
“Many people died here, even those who were not stealing fuel because this is a busy place,” said eyewitness Daniel Ngogo, quoted by Reuters news agency.
Local Police Chief Willbrod Mtafungwa said many of those killed were motorbike taxi drivers.
Pictures posted online show flaming wreckage scattered over a wide area and charred bodies lying on the ground.
On Sunday relatives grieved as coffins lined a football field. Some relatives took their relatives coffins to bury them in private funerals.