Emergency officials in Puerto Rico raced on Saturday to evacuate some 70,000 people after a rain-swollen dam failed in the latest disaster caused by Hurricane Maria.

With the death toll from the storm at 33 across the Caribbean, the National Weather Service office in capital San Juan Friday issued a flash flood warning for people living along the Guajataca River and said the 1920s earthen dam was in danger of collapsing altogether.

“All Areas surrounding the Guajataca River should evacuate NOW. Their lives are in DANGER!,” the service said in a tweet. Flooding has already begun downstream, it said.

Shortly thereafter, Governor Ricardo Rossello issued an order for some 70,000 people living in the area in the northwest of the island to get out.

According to the newspaper El Vocero, Public Safety Secretary Hector Pesquera said a drain that normally releases a stream of water from the dam in a controlled fashion had broken.

Instead the busted drain sent water gushing down a ramp-style conduit, eventually washing away huge chunks of soil from the grassy green slope of the dam, according to video on the WeatherNation website. 

However the flash flood warning was only due to last until 0600 GMT, the weather service said, suggesting that the river waters were receding.     

Puerto Rico was already battling dangerous floods after Hurricane Maria ravaged the island early Wednesday. Rescuers raced against time to reach trapped residents. 

Maria, the second major hurricane to savage the Caribbean this month and the most powerful storm to strike Puerto Rico in nearly a century, carved a path of destruction on Wednesday. The island remained entirely without electricity, except for emergency generators, two days later.

Telephone service was also spotty.

Rossello has called Maria the most devastating storm in a century.