Investigators are focusing on a clamp that may have failed, collapsing a support that held the women aloft by their hair in a "human chandelier."
The accident occurs as the American circus is making something of a comeback after being battered by years of animal-abuse allegations - and reveals the inherent contradiction at the heart of the business: The need to captivate paying audiences through breathtaking, death-defying feats, while at the same time ensuring that the performers are safe.
"There are absolutely inherent risks in what we do and how we train," said Marc Miller, managing director of the Philadelphia School of Circus Arts in Germantown, which instructs thousands of people in big-top arts.
But, he said, the school takes every possible precaution. Those ranges from regularly checking ropes for signs of distress to ensuring that staff members do not use ladders to check equipment connections near the ceiling. Instead, they go up on mechanical lifters.
After having taught an estimated 10,000 students - some for a day, others for years - the school has never had an injury due to equipment failure, Miller said.
These days, people no longer have to run away from home to join the circus. They can go to school and learn skills from professionals. Many seek instruction for a performance career, but also for fitness, self-confidence, and fun.
New Jersey has a circus school. New York has at least four. Florida State University has a big top on campus, teaching skills through its Flying High Circus, billed as one of two collegiate programs in the country.
Locally, the Greene Street school is a gym-size space filled with unicycles, static trapezes, juggling pins, ropes, mats, and a lyra, also known as an aerial hoop. Its programs range from one-day acrobatics parties for children to private lessons for serious-minded performers.
Many trainees will actually join a circus or help craft a living by performing in circus-like exhibitions.
"Your traditional one-night-stand tent circus is having a hard time, but Ringling Bros. is flourishing, and Cirque du Soleil is the biggest circus in the history of the world," said circus historian Fred Pfening III, a trustee and past president of the Circus Historical Society.
Sadly, Pfening said, circus accidents and tragedies are as old as the institution. They're almost part of American lore, remembered and retold in books and films.
The best known may be the Hartford circus tent fire that killed more than 160 people and injured nearly 700 others in 1944. The great Karl Wallenda - who once walked a tightrope across Veterans Stadium - fell to his death in Puerto Rico in 1978. Last year, Cirque artist Sarah Guillot-Guyard, 31, was killed after the rope wire that supported her broke.
Back in the mid- to late-1800s, it was common for circus troupes to lose one or two performers a season, often in train accidents, Pfening said. He is CEO of the Fred D. Pfening Co., which manufactures bakery machinery in Columbus, Ohio, but his love is the circus. His father owned and ran a circus when he was a boy.
"Everything is safer today, and everything is more regulated today," Pfening said. Still, "every few years, somebody is killed or seriously injured in a performance. . . . It's just a real unfortunate thing."
On Sunday, at the Dunkin' Donuts Center in Providence, eight performers called "hairialists" were hanging by their hair when the support frame collapsed. They were executing a movement in which six women hang by their hair on the edge of the frame, while two others hang in the center.
A video shows a curtain falling away to reveal the women hanging from the apparatus. Only seconds later, as they begin to perform, all fall to the ground and the apparatus lands on them.
Several witnesses said that at first, they thought the fall was part of the act.
"It's terrifying," said Lunny, who was teaching and working out at the Philadelphia school Monday. "It hits the community, because something could always go wrong."
Lin started his circus career in 1986 in the Fujian province of China. He vividly recalls an acrobatics accident in which a broken pole was driven into the chest of a performer, who barely escaped death.
"Nobody wants this to happen," he said, mulling the Rhode Island accident. "We try to make it safer."
This article contains information from the Associated Press.