At least 20 people have been killed in floods in northeastern Brazil, local officials said on Monday, as the region braced for more rain.

Home to about 15 million people, weeks of intermittent flooding have intensified in Bahia state in the last two days after a pair of dams collapsed, sending residents scrambling.

“Unfortunately, we’re living through the worst disaster that has ever occurred in the history of Bahia,” the state’s governor, Rui Costa, said on Monday on Twitter, adding that 72 municipalities in Bahia are in a state of emergency.

Teams of rescuers are trying to transport supplies and bring medical care to victims, the governor also said, but damage to bridges and highways has made those efforts more difficult.

The two dams that collapsed over the weekend were in the cities of Jussiape and Itambe.

Rescue workers have been patrolling in small dinghies around the city of Itabuna, plucking residents from their homes, including some who escaped through second-floor windows.

Manfredo Santana, a spokesperson for Bahia’s firefighting corps, told the Reuters news agency on Monday that emergency workers had rescued 200 people in three towns. The heavy currents of the swollen Cachoeira River complicated rescue efforts.

“It’s difficult to manoeuver even with jet skis,” he said. “Rescue teams had to retreat in certain moments.”

Bahia’s civil defence agency said on Monday afternoon that 20 people had died as a result of the floods in 11 separate municipalities.

The state government said a day earlier that more than 16,000 people had been left homeless by the flooding.

In televised remarks, Costa attributed the chaotic scenes in part to “errors that have been committed over the course of years”.

Newspaper O Globo, citing a state firefighting official, reported that authorities are monitoring an additional 10 dams for any signs they may collapse.

Scrutiny of public infrastructure and urban planning comes just a few years after the collapse of a mining dam in neighbouring Minas Gerais state killed some 270 people.

A government task force made up of military firefighters and police has been set up in badly-hit areas of Bahia to help respond to the disaster.

In the state capital of Salvador, weather officials said December rainfall has been six times greater than the average.

The heavy rainfall coincides with La Nina, a weather phenomenon that typically occurs every three to five years and leads to cooler Pacific Ocean temperatures than normal.