A support frame collapsed during a hair-hanging stunt at a US circus performance, sending eight acrobats falling to the ground.
Nine performers were seriously injured, including a dancer below, while others suffered less serious injuries.
The accident was reported about 45 minutes into the Ringling Brothers and Barnum and Bailey Circus' Legends show in Rhode Island.
Stephen Payne, a spokesman for Feld Entertainment, the parent company of Ringling Brothers, said the accident happened during an act in which eight performers hang "like a human chandelier" using their hair.
He said the metal-frame apparatus came free from its metal truss. The eight women fell up to 40 feet, landing on a dancer on the ground.
All the performers have been doing "some variation of this act for some time," Mr Payne said. The current incarnation of the act began in January, he said.
Providence public safety commissioner Steven Pare said officials and inspectors have not yet determined what caused the accident. He said none of the injuries appears to be life-threatening.
Roman Garcia, general manager of the Legends show, asked people to pray for the performers.
"Everybody's doing fine, everybody's at the hospital, everybody's conscious, everybody's doing pretty well," he said.
Rhode Island Hospital in Providence admitted 11 patients with varying injuries, including one in critical condition, spokeswoman Jill Reuter said.
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."
Video taken by audience members showed a curtain coming down, and several performers hanging around 25 feet in the air from an apparatus suspended from above.
Seconds later, as they began to perform, the women fell and the metal apparatus landed on them.
"It just went crashing down," said audience member Sydney Bragg, 14. "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 said she saw that the acrobats had fallen on top of at least one other performer on the ground, 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.
A Ringling Brothers aerial performer was killed in 2004 in Minnesota when she was twirling 30 feet in the air on long chiffon scarves and the material gave way.
An investigation has begun into the cause of the accident, which happened at the 11am local time performance yesterday, and several later shows were cancelled.