The death toll from a building collapse in Cameroon's business hub Douala rose to 37 on Monday, as neighbours recalled the structure's "failings" and "cracks", fearing more bodies lie under the ruins.

The four-storey block of flats collapsed onto another residential building in the north of the city overnight on Saturday.

One of the worst such tragedies in the country's history, it left 37 people dead and 21 injured, five in critical condition, a senior fire officer and the regional governor told AFP on Monday, warning that the toll could rise.

Cameroon's urban development minister Celestine Ketcha-Courtes, who visited the scene of the tragedy on Monday, told reporters that the ill-fated building "did not have planning permission".

Rescuers were still trying to clear the rubble with a digger after seeking survivors throughout Sunday and Monday, a resident told AFP.

Douala's Laquintinie hospital on Sunday said it had taken in 13 patients, two of whom -- a three-year-old girl and a woman aged 19 -- had died.

"The toll could still go up," said computer scientist Prosper Tchinda, who was one of the first on the scene on Sunday.

"There was one survivor who got out with just scratches and we found a baby safe and sound," he told AFP by telephone.

The 42-year-old lives a few minutes' walk from the block and said there had been "some sort of event with music going on when it happened".

Nathalie, who also lives in the area but did not want to give her full name, said the building had "failings" and was in a poor state.

"There were cracks in the wall and we felt it could collapse at any time," she said.

"It was not the sort of place you would want to live in."

Natalie said she went to the site immediately after hearing "a big noise", and confirmed that a party had been going on.

Tchinda said he was "very worried".

"There are so many buildings that don't meet the standards. Each one goes up built anyhow without any checks.

"You have the impression that the appropriate services at city hall are not doing their job," he added.

Five people died in similar circumstances in Douala in 2016 when authorities blamed the poor state of repairs and apparent violations of building regulations.

In June that year, local authorities identified 500 buildings in danger of collapse.