OKLAHOMA CITY (AP) — Engineers are investigating why five limestone panels that had been attached to the building being renovated in downtown Oklahoma City came loose and fell 22 floors to the street below.

No one was injured when the panels fell from the First National Center Sunday night, but three vehicles were damaged. A developer told The Oklahoman newspaper it's possible that water was able to get behind the stone after a fire on a higher floor, and that freezing weather may have popped the panels from their bolts.

A downtown street could be closed until Wednesday while workers dete...