"Two more bodies were found this afternoon," regional commissioner Saidi Mecky Sadicky told AFP, updating an earlier toll of 17 in the disaster that happened on Friday.
Several dozen people are still missing around the site, which was littered with huge chunks of concrete.
Eighteen people have been rescued alive from the remains of the 16-storey building, he said. However it is almost 24 hours since the last survivors were pulled out.
Hundreds of rescuers worked through the night in search of those still trapped in the rubble from the shell of the tower, which was being built near a mosque in the Kisutu area of Dar es Salaam.
Rescue work was slowed on Saturday afternoon after it started to rain.
Sadicky said between 60 and 70 people were reported to have been at or near the construction site on Friday morning, meaning that between 25 and 35 people could still be trapped.
Hundreds of people, including residents and army rescuers, clawed through piles of rubble in the hunt for survivors, alongside earthmovers and excavators.
"I thought there was an earthquake and then I heard screaming. The whole building fell on itself," witness Musa Mohamed told AFP on Friday shortly after the collapse
Sadicky said the rescue team was boosted on Friday night after the Chinese embassy told Chinese construction firms to provide additional earthmoving equipment.
Dozens of Chinese construction workers were at the site on Saturday instructing operators of excavators and forklifts that were sifting through the rubble.
Local residents turned out to supply rescuers with food, water and medication.
Tanzanian President Jakaya Kikwete visited the scene of the disaster in the coastal city and posted messages of condolence on his Twitter account.
"We pray for those who have been afflicted by this tragedy," he said. "We pray for togetherness in this time of need."