An explosion that caused alarm in Winnipeg's St. Boniface neighbourhood Wednesday night was the result of someone setting off fireworks, police said.

Police were called to the roof of a building on Marion Street around 10 p.m. after people in the area reported hearing an explosion.

Investigators found minor damage to the building, and located what they called a "suspicious device" on the ground nearby.

The area was cordoned off and the bomb unit called to the scene.

The device was later determined to be a commercial-grade pyrotechnic device.

No one was injured when the fireworks went off.