SAN JUAN (Puerto Rico) • Emergency officials in Puerto Rico raced yesterday to evacuate tens of thousands of people from a river valley below a dam which is on the verge of collapse under the weight of flooding in the aftermath of Hurricane Maria.

The potential calamity in the island's north-west was unfolding as residents struggled without electricity to clean up and dig out from the devastation left by Maria, which has killed at least 25 people across the Caribbean, according to officials and media reports.

Some 70,000 people live in a cluster of communities under evacuation, downstream from the earthen dam on the rain-swollen Guajataca River, Puerto Rico Governor Ricardo Rossello said in a late-afternoon news conference on Friday.

Residents of the area were being ferried to higher ground in buses, according to bulletins issued by the National Weather Service from its office in San Juan, the capital of the United States island territory.

Ms Christina Villalba, an official for the island's emergency management agency, said there was little doubt the dam was about to break. "It could be tonight, it could be tomorrow, it could be in the next few days, but it's very likely it will be soon," she told Reuters by telephone on Friday night. She said the authorities aimed to complete evacuations within hours.

Mr Rossello went to the municipality of Isabela on Friday night and told Mayor Carlos Delgado that an evacuation there was urgent, his office said in a statement.

Mr Rossello said the rain sparked by Maria had cracked the dam and could cause fatal flooding. Puerto Rico's national guard had been mobilised to help the police evacuate all necessary areas, he said.

People had begun leaving nearby areas, but a small community was refusing and Mr Rossello instructed the police to step in under a law that mandated them to remove the local population in an emergency, the statement said.

Ms Villalba could not say how many people had already been evacuated, or how the authorities were communicating with residents to organise the evacuation.

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 last Wednesday. The island remained entirely without electricity, except for emergency generators, two days later. Telephone service was also unreliable.

Roofs were ripped from homes and the landscape was littered with tangles of rubble, uprooted trees and fallen power lines.

REUTERS