The city of Medicine Hat, Alta., has declared a state of local emergency over fears of a potential breach of a reservoir.

Rapidly melting snow and flooding has officials worried that the dam that forms the Seven Persons Reservoir could breach.

The water level in Seven Persons Creek is expected to rise by up to 60 centimetres over the next several hours.

The city said 28 at-risk homes have been ordered evacuated, and as many as 500 more homes are currently under a voluntary evacuation order.

The state of emergency was issued just after 7 p.m. MT.

An evacuation centre has been set up in a ballroom at the Stampede Grandstand.