The death toll from floods hammering northeast Brazil rose to 20 on Monday, as the governor of Bahia state declared it the worst disaster in the state's history and rescuers braced for more rain in the coming days.

Much of Bahia, home to about 15 million people, has suffered from intermittent flooding for weeks, after a long drought gave way to record rains. Flooding in some areas intensified late on Christmas Eve and early on Christmas Day after a pair of dams gave way, sending residents scrambling for higher ground.

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

Bahia Governor Rui Costa said on Twitter that 72 municipalities were in a state of emergency.

"Unfortunately, we're living through the worst disaster that has ever occurred in the history of Bahia," he wrote.

Manfredo Santana, a lieutenant-colonel in Bahia's firefighting corps, told Reuters that emergency workers had rescued 200 people in just three nearby towns. The heavy currents of the swollen Cachoeira River complicated rescue efforts.

"It's difficult to maneuver even with jet skis," he said. "Rescue teams had to retreat in certain moments."

Bahia's civil defense agency said on Monday afternoon that 20 people had died in 11 separate municipalities.

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

The scrutiny of public infrastructure and urban planning comes just a couple years after the collapse of a mining dam in neighboring Minas Gerais state killed some 270 people.

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