Park service probes museum mishap

PHILADELPHIA -- The National Park Service is investigating what went wrong at the opening of the National Constitution Center, where a large wood and steel frame tipped over, injuring several.

The apparent accident on Friday was being investigated to exclude the chance that sabotage or vandalism were to blame, officials said.

The museum's opening ceremony was to have ended when people on stage pulled on ribbons attached to a frame. A screen was supposed to drop, revealing a piece of artwork. Instead, the frame came crashing down.

Forty-two people were on the stage, and a U.S. senator and a federal judge suffered minor injuries. U.S. Supreme Court Justice Sandra Day O'Connor narrowly missed being hit.

"We had a great celebration, it was perfect right up until about the last 10 seconds," Mayor John Street said Saturday on NBC's "Today" show.