(Updates death toll)
NAIROBI, March 30 (Reuters) - The death toll from the collapse of a building in Tanzania's commercial capital Dar es Salaam has climbed to 19, a senior official said on Saturday.
The building of more than 12 storeys, which had been under construction, collapsed on Friday morning near a mosque in the Kariakoo district around the city centre. Several cars were crushed by falling masonry.
Tanzania's buoyant economy has fuelled a building boom, especially in Kariakoo and the city centre. But the speed of construction has raised concerns about standards.
"Nineteen people have been killed so far and 17 were rescued alive, so this accounts for 36 people who were trapped in the collapsed building," Dar es Salaam Regional Police Commander Suleiman Kova told reporters at the scene.
"There is very little hope of finding any more people alive from under the rubble, but we are determined to recover all bodies so that they can be given a proper burial."
Witnesses said they believed construction workers were inside the building when it collapsed. Rescue workers sifting through the rubble on Saturday said two boys were also still missing.
Tanzanian President Jakaya Kikwete, who visited the scene on Friday, ordered authorities to act against responsible parties.
Kova said police had arrested four suspects, including the building owner. Police had previously said the owner in custody was also the contractor, but later said they were still looking for the building contractor. (Reporting by Fumbuka Ng'wanakilala; Editing by Edmund Blair and Andrew Roche)