Thousands of climbers huffed and puffed their way to the top of Toronto's CN Tower on Saturday morning to raise money for charity.

Groups and individuals of all ages cheered as they made it up the 72 flights of stairs for the Enbridge CN Tower Climb for United Way.

Louise Bellingham, vice president of marketing for the United Way said that the climb was sold out this year.

"We're expecting anywhere between 11,000 to 12,000 people to climb in the course of the event," Bellingham told CTV Toronto.

The 1,776 stairs of the tower takes participants about 30 minutes to complete.

"I work out six days a week and I thought I would kill this, but it's quite a challenge," said one participant.

Organizers said they expect to raise $2.1 million this weekend.

"It's been a really tough few years economically," Bellingham said. "People, I think, really want to do something and this is a wonderful way for them to participate in a hands-on kind of way."

With a report from CTV Toronto's Ashley Rowe