NAIROBI — Kenyan rescuers continued searching for survivors in the ruins of a collapsed residential building in a low-income section of Nairobi on Sunday, as officials said the death toll rose to 20.

Japheth Koome, the police chief for the capital, said 73 people were missing.

Authorities said the first floor of the building sank into the ground after heavy rains, and the structure collapsed Friday. The building, next to a river, had been declared unfit for human habitation by Kenya’s National Construction Authority but was not torn down.

Bribe-taking officers in the county government are responsible for allowing contractors to bypass building codes, Nairobi governor Evan Kidero said. He vowed to fire those responsible. The building’s owner obeyed police orders and turned himself in for questioning, Koome said.

“People who’ve died in Huruma have died an unnecessary death. That death is a product of corruption. . . . Someone is paid $10,000 or $20,000 to approve the building that cost the lives of Kenyans,’’ nominated legislator Johnson Sakaja said.

Kenyan military personnel led the rescue operation using heavy machinery to remove concrete slabs. About 300 residents of two adjacent buildings, also built close to the river, were evacuated.

Taking advantage of a high demand for housing in Nairobi, some property developers bypass building regulations to cut costs and maximize profits.

President Uhuru Kenyatta last year ordered an audit of all the country’s buildings to see if they are up to code after eight buildings collapsed, killing at least 15 people.

The report from the audit by the National Construction Authority found that 58 percent of buildings in the capital are unfit for habitation. The majority of Nairobi’s estimated 4 million people live in low-income areas or slums.

Associated Press