A massive fire in the William Whyte area has left at least 20 people without a place to live.

Shortly after 7 a.m. Sunday, fire crews responded to a three-storey apartment complex in the 300 block of Mountain Avenue.

Heavy black smoke and flames were seen pouring out of the structure when crews arrived at the scene.

Firefighters battled the fire from the interior before they were forced out due to deteriorating conditions. They transititoned to a defensive attack using aerial ladders and hand lines.

A neighbouring home was evacuated as a precaution.

One person from the apartment building was assessed and treated at the scene.

The City of Winnipeg's Emergency Social Services team responded to the scene to help the displaced residents find alternate temporary housing.

The building is expected to be a complete loss. The cause of the fire is under investigation.