Ottawa Police have closed Wellington Street after a crane operator suffered a medical condition, and dropped lumber onto the street below.
Ottawa Fire Chief Kim Ayotte Tweeted "High Angle Rescue operations underway." and posted a photograph of crews preparing to scale the crane.
There is damage to cars, but no injuries to anyone on the ground, Police say.
Witnesses tell CTV News Ottawa firefighters are working to get the crane operator safely onto the ground.
Wellington Street is closed just east of Parkdale Avenue.
CTV's Megan Shaw is at the scene and will have more shortly.