A Utah town near the south entrance of Zion National Park is being evacuated, amid fears that a dam may fail on the Virgin River.

The National Weather Service says Trees Ranch Dam, just south of the park, could be breached Tuesday afternoon.

St. George assistant city manager Marc Mortensen says residents in Rockville have been evacuated.

Residents of nearby Virgin had left their homes but returned Tuesday. But Mortensen says they may be evacuated again if the dam breaks.

The national park has also been closed. Guests at the Zion Lodge and campers have been evacuated.

The mayor of St. George declared a state of emergency and in Arizona, Mohave County declared an emergency because of flooding in the Beaver Dam and Littlefield areas.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

SALT LAKE CITY (AP) — Two Utah towns near the south entrance of Zion National Park are being evacuated, amid fears that a dam may fail on the Virgin River.

The National Weather Service says Trees Ranch Dam, just south of the park, could fail Tuesday afternoon.

Officials say residents in Rockville and Virgin have been evacuated. Rockville has about 250 residents and Virgin, around 570

The national park has also been closed. Guests at the Zion Lodge and campers have been evacuated.

The Washington County sheriff's office says flooding wiped out one of two bridges to the southern Utah town of Gunlock, more than 40 miles east of Zion, and several roads are closed.

Mayor Daniel McArthur also declared a state of emergency in St. George, downstream about 40 miles.