The century-old Wahiawa dam, located in the north of Hawaii's third largest island, which is home to the state capital Honolulu, "is at imminent risk of failure," the local emergency management agency warned on Friday

There was "potential life-threatening flooding" in areas below the dam, it added

Hawaii Governor Josh Green said torrential rains have caused "serious flooding" and brought water in the reservoir to dangerous levels, prompting authorities to issue the alert

"Lots of people had to evacuate. We've evacuated the whole region now," Green said on social media

The National Weather Service reported particularly dangerous conditions in northern Oahu