The failure of a 5-inch steel D-ring recognised like a carabiner might have been the reason for a mishap in exce s of the weekend that hurt nine members of a Ringling Bros. and Barnum & Bailey acrobatic troop. « It was a single piece of equipment that failed, » Providence, R.I., fire investigator Paul Doughty told reporters. The incident occurred in Providence on Sunday when the support apparatus for an aerial stunt suddenly gave way, dropping performers to the ground. 9 customers of the troop were hurt and two others were hurt on the ground. But The A sociated Pre s says: »Providence Public Safety Commi sioner Steven Pare stopped short of saying the broken carabiner was the reason for Sunday’s accident. « He said federal workplace safety investigators were trying to determine why it snapped.  » ‘We don’t know if it was metal fatigue, if it wasn’t properly positioned or something else,’ he added. ‘We just don’t know.’ « CNN says: »The carabiner was rated for about 10,000 pounds, and the weight of the performers and the rig that fell was about 1,500 pounds, he said. « Doughty declined to say if the rigging appeared safe. But Providence Fire Chief Clarence Cunha said his crews would not rely on a single carabiner for safety. »