SAN JUAN, Puerto Rico (AP) - Puerto Rican authorities are scrambling to evacuate as many as 70,000 people who are downstream of a failing dam.
  
More than 15 inches of rain fell on the mountains surrounding the Guajataca (wa ha TA ca) Dam in northwest Puerto Rico after Hurricane Maria left the island Wednesday afternoon, swelling the reservoir behind the nearly 90-year-old dam.
  
Authorities launched an evacuation of tens of thousands of people living downstream, sending buses to move people away and sending frantic warnings on Twitter that went unseen by many in the blacked-out coastal area. Officials say between 50,000 and 70,000 people may need to be evacuated.
  
The national weather service first learned of a "contained breach" during a Friday afternoon inspection. The Puerto Rican government confirmed it is more than a fissure, and concluded that the dam is actually failing.
  
Officials say they don't know how much time residents have to evacuate.