Authorities trying to determine what caused a support frame to collapse during an aerial hair-hanging stunt during a circus performance today focused on a broken clip.

The snapped carabiner was found today, as crews investigated the accident that sent eight acrobats crashing to the ground and injured 11 people.

At least three of the injured remained in critical condition today, Rhode Island Hospital officials told ABC News.

The 4- to 5-inch steel clip was found in three pieces on the ground with its spine snapped, Providence Public Safety Commissioner Steven Pare said.

We don’t know if it was metal fatigue, if it wasn’t properly positioned or something else,” he said. “We just don’t know.”

The Occupational Safety and Health Administration is investigating and will make the final determination of whether the carabiner was to blame for the collapse, he said.

The incident happened about 45 minutes into a performance of the Ringling Bros. and Barnum & Bailey Circus’ legends show Blue Unit at the Dunkin’ Donuts Center in Providence, R.I.

It was witnessed by an audience of about 3,900, many of them children.

“Everybody’s doing fine, everybody’s at the hospital, everybody’s conscious, everybody’s doing pretty well,” Roman Garcia, general manager of the Legends show, said after the accident.

See the video and get the rest of the story via Circus Accident Investigation Focused on Snapped Carabiner – ABC News.