An inquest that will examine two deadly house fires, including the fire that killed members of the Dunsmuir family in East Gwillimbury, is now underway.

It was exactly three years ago when fire tore through a home in Sharon, Ont. claiming the lives of four family members.

Kevin and Jennifer Dunsmuir and their teenage sons Cameron and Robert were trapped inside the master bedroom and died.

In a Toronto courtroom, the coroner's counsel opened an inquest into the deaths on Tuesday.

“Their deaths are tragic and we have to examine what happened," says lawyer Frank Giordano. "We’re here to make the community better, to make it safer."

Investigators with the Ontario Fire Marshal’s Office said the fire was likely caused by a clogged dryer vent on the main floor. There was no working smoke detector on the main floor and by the time the second floor detector went off – it was too late.

"The fire conditions were such that it made survival by the occupants and rescue by emergency responders untenable,” the OFM investigator said in August 2014.

At the inquest, jurors will hear testimony from first responders, neighbours and investigators.

The purpose is not to lay blame, but rather to look into what happened, the response from emergency services, the fire code and all aspects of fire safety. 

The jury could also make recommendations to help prevent future fire deaths.

East Gwillimbury's fire chief is hoping the inquiry will lead to something positive.

"We’re interested in how we can do service better if that is the case and specifically public education and the enforcement of it," says fire chief Phil Dawson.

This same inquest is also examining a fatal fire in Whitby in 2012 that claimed the lives of three teens. The jury is hearing testimony on the Whitby case first.

The inquest is expected to last eight weeks and the jury will hear testimony from more than 50 witnesses.