The four-storey block came down at around 9:00 am (0600 GMT) on Saturday in the east African country’s busy Kariakoo market, in the centre of the commercial capital Dar es Salaam. Thirteen people have been confirmed dead, the presidency said Sunday, up from an initial figure of five. At least 84 people had been rescued from the rubble, President Samia Suluhu Hassan said

Dar es Salaam regional commissioner Albert Chalamila said earlier Sunday that more people were still trapped in the basement floor of the shattered building, without specifying how many.

Fire brigade chief John Masunga said the search and rescue operations had been hampered by the many walls making up the structure of the building.

It is not clear why the commercial building collapsed but witnesses told local media that construction to expand its underground business space began on Friday.

In the immediate aftermath of the collapse, hundreds of first responders used sledgehammers or their bare hands to search the rubble for hours before cranes and other heavy lifting equipment were brought in.

The incident has renewed criticism over unregulated construction in the Indian Ocean city of more than five million people. One of the world’s fastest growing cities, Dar es Salaam has been the scene of a frenetic property boom with buildings shooting up quickly, often with scant regard for regulations.