So many asylum seekers are crossing into Canada from the United States that Montreal's Olympic Stadium has been opened to house them.

The first groups were bused to the stadium on Wednesday. Cots are set up in the windowless, domed facility. The mainly Haitian migrants will stay until they get government financial assistance.

Francine Dupuis, head of a Quebec government-funded programme that helps asylum seekers, said a maximum of 450 people will be housed temporarily. She said her organisation helped 448 people in June and 1,174 in July, far more than previously.

"We are really stretched, really stretched," Dupuis said. "It's much more than we have ever seen."

Ninety percent are Haitians. The US is weighing ending a programme that granted Haitians "temporary protected status" after Haiti's 2010 devastating earthquake. If the programme is not extended, as many as 60,000 Haitians in the United States could be sent back to their homeland.