The College Lake Dam exceeded its capacity after up to 6in (15cm) of rain fell on Thursday evening, Lynchburg Water Resources Department said.

The city of Lynchburg is the closest settlement downstream of the structure.

If the dam fails completely, 17ft (5m) of water could flood it in seven minutes, the National Water Service said.

Lynchburg has a population of about 80,000 and lies in the Blue Ridge Mountains.

Dozens of households have been told to evacuate

Officials have warned residents not to drive down flooded streets, adding that the floodwater may contain debris.

Local outlet WDBJ7 said a number of people whose homes were deemed to be at risk had been evacuated to nearby schools, along with their pets. They have been advised not to go home for at least 24 hours.

Some 124 households have been urged to evacuate, Lynchburg's Department of Emergency Services said.