The Lincoln Alexander Parkway at Upper Ottawa Street was a dangerous stretch of road on Saturday.
Hamilton Police responded to reports of rocks and pieces of lumber on the road from curb to curb.
Drivers were pulling over on the side of the road with damage to their vehicles caused by the debris, city police said.
After further investigation, officials say the rocks and fragments were placed on purpose and they are now looking for suspects.
No one was injured and the city has cleaned the area.