(CBS News) - SAN JUAN, Puerto Rico -- 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.
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."
The government called the situation "extremely dangerous." Communications to outlying areas of the island have been hampered by the storm.
"It's a structural failure. I don't have any more details," Gov. Ricardo Rossello said from the capital, San Juan. "We're trying to evacuate as many people as possible."
All across the battered island, residents feared power could be out for weeks -- or even months -- and wondered how they would cope. Some of the island's 3.4 million residents planned to head to the U.S. to temporarily escape the desolation. At least in the short term, though, the soggy misery will continue: additional rain -- up to 6 inches -- is expected through Saturday.