(CNN) All people living near the Guajataca River in northwest Puerto Rico should evacuate immediately because of an "imminent dam break," the National Weather Service in San Juan said Friday afternoon.

"All Areas surrounding the Guajataca River should evacuate NOW. Their lives are in DANGER! Please SHARE!" an earlier tweet said.

All Areas surrounding the Guajataca River should evacuate NOW. Their lives are in DANGER! Please SHARE! #prwx — NWS San Juan (@NWSSanJuan) September 22, 2017

About 70,000 people in the area of the Guajataca Dam have been told to evacuate, National Guard spokeswoman Yennifer Alvarez told CNN's Leyla Santiago. Buses have been brought in to help people leave.

Puerto Rico Gov. Ricardo Rossello said on Saturday afternoon that the dam was holding up, but residents should still evacuate the area until further notice.

"We don't know how much longer it will hold," said Rossello. "The structure has been significantly compromised."

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