An Ornge air ambulance helicopter has been grounded outside Thunder Bay following an incident that left its rotor blades damaged.

A spokesperson for the Ontario air ambulance system, Steve Robinson, said the blades struck a tree during a landing to pick up a patient at a residence south of Kakabeka Falls in Gillies Township on Sunday afternoon.

Robinson said the helicopter was able to land and the two pilots and two paramedics aboard were not injured.

The paramedics later accompanied the patient to Thunder Bay hospital in a land ambulance.

'You probably wouldn't notice it'

Robinson said the Sikorsky S-76 is out of service until investigations and repairs are completed.

"It's blade damage only. If you looked at it from a few feet away you probably wouldn't notice it until you get up close," he told CBC News.

An official at the federal Transportation Safety Board said Monday the board had not yet decided whether to send an investigator to the scene, but Robinson said the TSB had released the scene to Ornge. 

The damaged unit is the only Ornge helicopter in the Thunder Bay area, however Ornge also has two fixed-wing aircraft as well as contracted aircraft available to provide air ambulance service in the region.