More bodies, including those of two children, have been pulled out of the rubble of the building that collapsed in Tanzania's economic capital of Dar es Salaam, bringing the toll to 17, a local government official said Saturday.

"So far the number of people who are dead is 17. This includes two children," regional commissioner Saidi Mecky Sadicky told AFP.

He said rescuers were still looking for two children.

Several dozen people in all are still missing around the site, which was littered with huge chunks of concrete.

"The operation is still going on but we have very little hope to find anyone alive," Sadicky said.

Eighteen people have been rescued alive from the remains of the 16-storey building that came crashing down on Friday morning, he said.

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 Tanzania's economic capital.

Sadicky said between 60 and 70 people were reported to have been at or near the construction site 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 Friday evening after the Chinese embassy told Chinese construction firms to provide additional earthmoving equipment.

Dozens of Chinese construction workers were at the site Saturday morning 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," he added.

In 2008, another building that collapsed in Dar es Salaam claimed at least four lives.

"It looks like the city authorities are not serious with the enforcement of construction and housing laws. Incidents of collapsing buildings are on the increase," resident Rashid Abdallah said.

The ill-fated building is a joint project between the state-owned National Housing Corporation and Ladha Construction Limited being built under a private public partnership arrangement.

Sadicky said investigations into the cause of the accident are underway and police are holding the owners of the building and officials from both the construction firm and Dar es Salaam City Council for questioning.

Kikwete ordered on Friday that those responsible should be taken to task.