@ NYTimes.com, 7:52 pm

A dam in northwestern Puerto Rico suffered structural damage on Friday, the governor said at a news conference, prompting evacuations of areas nearby in the aftermath of Hurricane Maria.

“Close to 70,000 is the estimate of people that could be affected in the case of a collapse,” the governor, Ricardo Rosselló, said about the Guajataca Dam, which is operated by the Puerto Rico Electric Power Authority. “We don’t know the details. It’s time to get people out.”

The news about the dam was a dramatic sign that the scale of troubles left behind by the storm were just being understood. Power remained out and phone service was still limited. On Friday night, the governor was flying over to the dam area to see how serious the risk might be, said a spokeswoman for the Puerto Rico Emergency Management Agency. 

A flash flood warning was previously issued by the National Weather Service for the municipalities of Isabela and Quebradillas, in the immediate areas of the dam. “This is an extremely dangerous and life-threatening situation,” the service said in an advisory.

Messages sent to the power authority about the condition of the dam were not immediately returned.bThe National Guard has been activated in the area, the governor said [....]