Quebec’s government said Sunday it would launch a public inquiry to determine why an overpass collapsed north of Montreal, crushing five people to death.

Visiting the accident site Sunday, Quebec Premier Jean Charest gave his condolences to the families of the victims and said an inquiry by a former provincial leader would seek to shed light on the disaster.

“We don’t know how this happened,” Charest said. “The initial info we have leads us not to be able to understand how the bridge fell. We’re going to want to find out how this happened and why this happened.”

There appeared to have been some advance warning signs of trouble with the overpass in Laval before Saturday’s collapse, which also injured six people. One witness told TVA television network that he noticed the road had sunk an inch or two when he drove on the overpass minutes before the collapse and he called emergency dispatchers.

Transport Quebec, the province’s transportation ministry, also heard about an hour before the accident that some pieces of concrete were falling off the overpass, said spokeswoman Josee Seguin. She said Transport Quebec then issued an advisory to traffic reporters on the debris and an inspector from the agency was sent to the site, but it remained open.

Not long after that, a 65-foot stretch of the viaduct collapsed, sending several vehicles crashing onto Highway 19 below.