A chunk of concrete that struck a car in Montreal Thursday afternoon did not fall off an overpass, city officials say.

A passenger was treated for minor injuries. ((CBC))

A 29-year-old man, who was a passenger in the car, sustained minor injuries after the grapefruit-sized chunk of concrete broke the windshield around 4:20 p.m.

Police closed Papineau Street near Saint-Grégoire Street for several hours while engineers examined the structure.

Investigators will now look at whether someone threw the concrete off the overpass.

Montreal authorities closed Papineau in both directions between Rosemont Boulevard and Saint-Grégoire Street following the incident.

The overpass is travelled by CP Rail freight trains. ((CBC))

CP Rail tracks run across the overpass, but the railway is not responsible for its maintenance, said spokesman Ed Greenberg.

The railway sent officials to the scene to help investigate, and postponed trains scheduled on the line.

It was initially thought the incident was another example of the decay plaguing Montreal's road network.

In July, a concrete beam in the Ville-Marie Expressway tunnel crashed on the road, prompting transport officials to shut the heavily travelled artery for emergency repairs.