MADISON, Wis. (AP) — A concrete slab somehow fell off the University of Wisconsin System headquarters building's facade and plunged three stories to the sidewalk.

The Wisconsin State Journal reported the slab fell from Van Hise Hall on the UW-Madison campus Sunday. Part of the slab shattered.

The other part fell on a dumpster parked in front of the building's main entrance. No one was hurt.

UW-Madison officials are investigating why the slab fell. They say no construction work was going on that would have caused it.

The dumpster was placed in front of the building for use during a restroom renovation this week.