Nearly 70,000 people from western Puerto Rico were being evacuated after a 90-year-old dam was damaged by Hurricane Maria, The Guardian reported. Many parts of Puerto Rico are flooded and more than 3 million people do not have electricity.

A crack appeared on the Guajataca dam on Friday, leading to risks of flash floods. Residents of the municipalities of Isabela and Quebradillas have been told to evacuate. “It’s a structural failure. I don’t have any more details,” Governor Ricardo Rosselló said from the United States territory’s capital, San Juan. “We’re trying to evacuate as many people as possible.”

The National Weather Service in San Juan also said that people living in the areas surrounding the Guajataca river should be evacuated immediately as their lives were in danger. It instructed residents to move to higher ground immediately. “Preliminary results indicate that a full breach would result in large peak flows that would reach the coast in under 12 hours,” the weather service alert said.

Anthony Reynes, a meteorologist with the US National Weather Service, was quoted as saying that there was no indication about how this crack could evolve, or how long it would take. “That is why the authorities are moving so fast...It is a really, really dire situation.”

Hurricane Maria was the second major storm to hit Puerto Rico in about a month. Its Governor Ricardo Rosselló had said Maria was the “most devastating storm to hit the island this century, if not in modern history”. Before that, the island had not seen a Category 5 storm since San Felipe II in 1928, which killed more than 300 people.