A 28-year-old worker is fighting for his life in hospital after he fell off the roof of a building at Saint Paul University.

Paramedics say the man fell at about 3:20 p.m. Wednesday from a building at the school on Main Street.

He suffered life-threatening head injuries and fractures to his upper legs and ribs.

The man, who also suffered a collapsed lung that was re-inflated by paramedics, was repairing the roof and fell between 12 and 15 metres to the ground, paramedics said.

He was conscious when he arrived at hospital and he is currently listed in critical condition.

The Ontario Ministry of Labour is investigating.