Story highlights No deaths or injuries reported, emergency management official says

State of emergency issued for city

Residents asked to make residences with 'X' if they relocate

Canadian prime minister says military helicopter will help with rescues, evacuations

As many as 100,000 residents of Calgary, Canada, could face evacuation because of flooding, the director of emergency management said early Friday.

Mandatory evacuation orders have been issued for 20 communities, Bruce Burrell said. Parts of of southern Alberta face rising floodwaters and the possibility of more rain.

The levels of the Bow and Elbow rivers are expected to peak overnight, but not drop until late Saturday at the earliest, he said.

"I have never experienced any flooding of this magnitude," he added.

There have been no initial reports of deaths or injuries.

Canadian Prime Minister Stephen Harper said military assets, including helicopters, have been deployed to assist local emergency officials with rescue and evacuation efforts.

"Our thoughts and prayers are with those families who have been affected by the serious flooding in Calgary and Southern Alberta," Harper said, adding that "any and all possible assistance" would be provided by the federal government.

A state of emergency was in effect for Calgary, according to a news release from the city. Police and fire officials were driving through communities, broadcasting the evacuation order over loudspeakers. Residents were being asked to mark their homes with an "X" to indicate they had evacuated.

The news release said the level of the Elbow and Bow Rivers had risen significantly.