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CALGARY- A huge boom startled northwest residents on Tuesday evening, sparking an investigation by emergency crews.

The loud noise happened around 5 p.m. and could be felt in communities like Hidden Valley, Silver Springs, Ranchlands, Edgemont and Hawkwood.

Calls flooded into 911, with people reporting a shockwave that shook their homes.

Fire crews and police went out to investigate, but so far have not determined where the noise came from.

We are aware of reports concerning the sound of an explosion in N.W., #Calgary and have units searching for a cause #yyc — Calgary Police (@CalgaryPolice) March 5, 2014

They were looking into the possibility that it came from the Lafarge plant, where there was a similar incident back in November. That case turned out to be a permitted blast in their gravel pit.

However, a Lafarge spokesperson says no blasting took place at their site on Tuesday.

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Fire crews also told Global News they were looking into the possibility of the noise being caused by frost quakes, which are caused by a sudden cracking action in frozen soil or rock saturated with water or ice.

http://storify.com/globalcalgary/large-boom-startles-residents-in-north-calgary