Four people are in hospital with injuries after a townhouse exploded in Kitchener Wednesday night.

Emergency crews responded to Elm Ridge Drive, in the area of Queen's Boulevard and Fischer-Hallman Road, around 11:30 p.m.

Police confirmed that an explosion occurred inside a residence and caused "extensive damage." Neighboring units also sustained structural damage from the explosion.

"The fence and windows facing the street, first floor and second floor are shattered," read a statement from Waterloo Regional Police. "Debris from the house is also scattered around the yard, including a propane barbecue tank and a bicycle."

One man and one woman were transported to an out-of-region hospital with serious injuries. Two children were transported to a local hospital with minor injuries.

A Grand River Transit bus was brought in to provide shelter for displaced residents. Police say the Red Cross will also provide assistance.

The Ontario Fire Marshal has been called in to investigate. The cause of the explosion has not yet been determined.