A passenger train collided with a double-decker city bus in Ottawa today, killing six people and critically injuring 11 others.

Witnesses said the bus went through a closed crossing barrier.

It was Canada’s worst train accident since an oil train derailed and exploded in a Quebec town in July, killing dozens of people.

A number of bus passengers were injured, Ottawa Fire spokesman Mark Messier told CP24 television. Via Rail posted a message on Twitter saying there were no reports of major injuries to passengers or crew on the train.

Canadian Prime Minister Stephen Harper posted a message on Twitter saying he was deeply saddened by the accident and his thoughts and prayers were with the families of those involved.

The crash occurred in the west end of Ottawa, Canada’s capital city.