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Investigators looking into why circus acrobats fell to the ground during an aerial stunt in Rhode Island on Sunday -- which has left two performers in critical condition -- have found that a clamp snapped, a public safety official says.

"We have identified a clamp that snapped that held them to the rafters, and it failed," Providence Public Safety Commissioner Steven Pare told WPRO-AM a day after a support frame collapsed during the Ringling Bros. and Barnum & Bailey circus.

A Rhode Island Hospital spokesperson told Fox News on Monday morning that among the 11 injured in the accident, two performers -- Dayana Costa and Julissa Segrera -- are in critical condition. Three others -- Stefany Neves, Viktoriya Medeiros and Viktorila Liakhova -- were listed in serious condition. Samantha Pitard, Svitlana Balanicheva and Widny Nevas were listed in good condition.

The names and conditions of three others injured in the accident haven't been released. None of the injuries appear to be life-threatening, according to Stephen Payne, a spokesman for Feld Entertainment, the parent company of Ringling Bros.

The accident was reported about 45 minutes into the Ringling Bros. and Barnum & Bailey Circus' 11 a.m. Legends show at the Dunkin' Donuts Center in Providence, R.I. It was witnessed by an audience of about 3,900, many of them children.

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    "They've used this act many times. Unfortunately this particular clamp failed. It snapped off. We have it, we're analyzing it, we're seeing why it happened to ensure it doesn't happen in the future. That's all part of our focus," Pare told WPRO.

    Investigators from the federal Occupational Safety and Health Administration are probing the accident, along with local authorities.

    Eight of the injured were members of the circus' Medeiros troupe, and are from the United States, Brazil, Bulgaria and Ukraine, according to the circus' website.

    Payne said Kenneth Feld, the chief executive of Feld Entertainment, and his daughter Nicole, a circus producer, flew to Providence on Sunday night and was at the hospital visiting with the performers.

    The accident happened during an act in which eight performers hang "like a human chandelier" using their hair, according to Payne.

    He said the metal-frame apparatus from which the performers were hanging came free from the metal truss it was connected to. The eight women fell 25 to 40 feet, landing on a dancer on the ground.

    Video taken by audience members shows a curtain dropping to reveal several performers hanging from an apparatus suspended from above. Seconds later, as they begin to perform, the women fall, and the metal apparatus lands on them.

    "It just went crashing down," said audience member Sydney Bragg, 14, of North Kingstown. "Everyone was freaking out. We heard this huge clatter and then we just heard the girls scream."

    She said spotlights were on the performers at the time, but all the lights went out after the fall.

    Rosa Viveiros of Seekonk, Mass., said she saw that the acrobats had fallen on top of at least one other performer below, a man who stood up with his face bloodied. The acrobats remained still and did not get up, she said.

    "We thought it was part of the circus," said her husband, Joe.

    The couple attended the circus with their 6-year-old grandson and 9-year-old niece.

    "Everyone was in shock," Rosa Viveiros said. "It was pretty overwhelming to see that."

    Roman Garcia, general manager of the Legends show, asked people to pray for the performers.

    The hair-hanging stunt is described on the circus' website as a "larger-than-life act" featuring eight female performers.

    "These 'hairialists' perform a combination of choreography and cut-ups including spinning, hanging from hoops, and rolling down wrapped silks, all while being suspended 35 feet in the air by their hair alone," the website says. "In this hair-raising act, audiences will even see the weight of three girls held aloft by the locks of only one of these tangled beauties."

    The circus began performances in Providence on Friday. The Dunkin' Donuts Center canceled two shows scheduled for later Sunday and two others Monday have been allowed to proceed without any aerial stunts, MyFoxBoston.com reported.

    A Ringling Bros. aerial performer was killed in 2004 in St. Paul, Minn., when she was twirling 30 feet in the air on long chiffon scarves and the material gave way.

    Click to read more from MyFoxBoston.com.

    The Associated Press contributed to this report.