Early on Monday authorities said nine bodies had been retrieved from the crash site and transported to a nearby health centre "for further post-mortem analysis and DNA profiling"
Another body was found trapped under the truck, police said.
Nine more people injured in the accident later died from their wounds, police spokesman Fred Enanga told Reuters news agency.
The tanker was on its way from Kenya to the Democratic Republic of the Congo, police said.
The accident happened at Kyambura trading centre in Rubirizi district, according to the Daily Monitor newspaper.
More than 30 shops were burned, the newspaper added.
The police said two taxis, carrying at least 20 people, were among the damaged cars, without mentioning their fate.