In just a few seconds, a controlled implosion reduced Ottawa's historic Sir John Carling building to a massive pile of rubble early Sunday morning.

The former Agriculture Canada building was imploded just before 7 a.m. Sunday in front of a crowd of curious onlookers. As the 11-storey building came down and plumes of white smoke billowed in the air, the crowd could be heard applauding and cheering.

About 400 kilograms of dynamite were used to bring down the building, at a cost of about $4.8 million.

The building had served as the headquarters for Agriculture and Agri-Food Canada since 1967. By next summer, the area where the building once stood should be landscaped.

Spectators who had gathered to watch the implosion said it was quite the sight. They were kept 300 metres away from the building due to safety concerns.

"It's sort of unreal. I mean, you've seen it many times in videos, but to see it in real (time) and then to smell the smoke…. it's quite impressive," spectator Desmond Walsh told CTV Ottawa.

Others said they were shocked at how quickly the building came down.

"If you looked down for a second and looked back up it was gone," one male spectator said.

Idaho-based Advanced Explosives Demolition was charged with bringing the building down.

Advanced Explosives' Lisa Kelly and her husband Eric travel the world imploding buildings. They are one of only a handful of companies that do this kind of work.

Last week, as the company prepared the building for implosion, Kelly told CTV Ottawa the work required a lot of skill and precision.

"It's an art, a highly skilled profession," she said. "It's very dangerous and a lot of licensing is required to make sure it comes out OK."

Onlookers in Ottawa took photos and videos of the implosion. Here is a sampling of what they saw:

With a report from CTV Ottawa's Claudia Cautillo