SAN JUAN, Puerto Rico (CBSNEWS) – The National Weather Service in San Juan said Friday that the northwestern municipalities of Isabela and Quebradillas, home to some 70,000 people, were being evacuated with buses because the nearby Guajataca Dam was failing after Hurricane Maria hit the U.S. territory.

Maria poured more than 15 inches of rain on the mountains surrounding the dam, swelling the reservoir behind it.

Details remained slim about the evacuation with communications hampered after the storm, but operators of the dam reported that the failure was causing flash-flooding downstream. The 345-yard dam holds back a man-made lake covering about 2 square miles and was built decades ago, U.S. government records show.

“Move to higher ground now,” the weather service said in a statement. “This is an extremely dangerous and life-threatening situation. Do not attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order.”

“Act quickly to protect your life,” it added. “Buses will be evacuating people from these areas.”

*READ MORE AT CBSNEWS.COM*

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