I n 1997, a 13-year-old girl and her family stopped to watch an explosive demolition of an abandoned hospital in Australia. She was killed by flying debris. "Almost overnight, implosions worldwide ceased being actively promoted as spectator events," wrote Brent L. Blanchard, operations manager for consultant Protec Documentation Services, Rancocas Woods, N.J., in his history of the demolition technique.

Now there is a sad new chapter. California officials are investigating what went wrong during the Aug. 3 implosion of a Pacific Gas & Electric Co.-owned power- plant in Bakersfield that propelled shrapnel more than 1,000 ft toward a large crowd of spectators, injuring several and partially severing one man's leg.