Residents of Newport, Tennessee, have been ordered to evacuate the city “immediately” as heavy rains and flash flooding from Hurricane Helene move north.

Cocke County Mayor Rob Mathis wrote on his Facebook page just before 3 p.m. EST on Friday that the Waterville Dam “has suffered a catastrophic failure” and ordered the “immediate evacuation of all of downtown Newport.”

About half an hour later, Mathis announced that he had declared a state of emergency for the county, which is about 60 miles east of Knoxville.

It’s unclear what caused the damage to the dam, although officials in eastern Tennessee have warned of devastating flooding in the area. Mathis wrote in a post earlier Friday that “all county and city emergency resources are currently fully engaged in water rescue and evacuation operations.”

“We are still several hours away from the expected high water mark,” said the message, which Mathis posted at 11:32 a.m. EST. “If water rises near you, please do not wait for the water to reach you. Make escape plans BEFORE you need help.”

This is a developing story and will be updated with additional information.