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This undated photo released courtesy David Fox shows acrobat Sarah Guillot-Guyard, 31, who was pronounced dead at a hospital late Saturday night, June 29, 2013 after falling about 50 feet from the show's stage during a production of "Ka" at the MGM Grand. The founder of Cirque du Soleil says his tight-knit performance company is "completely devastated" after the veteran acrobat died in Las Vegas over the weekend in a fall witnessed by the audience. (AP Photo/Courtesy David Fox)

LAS VEGAS -- The founder of Cirque du Soleil says his tight-knit performance company, renowned for extravagant shows that challenge the boundaries of the body and the stage, is "completely devastated" after a veteran acrobat died in Las Vegas in a fall witnessed by the audience.

Coroner's officials said Sarah Guillot-Guyard, 31, was pronounced dead at a hospital late Saturday night shortly after falling about 50 feet from the show's stage during a production of "Ka" at the MGM Grand.

"I am heartbroken," Cirque du Soleil founder Guy Laliberte said in a statement. "We are reminded with great humility and respect how extraordinary our artists are each and every night. Our focus now is to support each other as a family."

While Cirque performers defy gravity every show -- soaring over audiences, scaling vertical walls and dangling aloft in aerial ballets -- the incident was the first stage casualty in the company's 29-year history, according to Cirque spokeswoman Renee-Claude Menard.

Witnesses told the Las Vegas Sun that the accident occurred during a fight scene near the end of the "Ka," which combines acrobatics with martial arts and puppetry and tells the story of two imperial twins on a quest to reclaim their Far East palace from evil warriors.

Visitor Dan Mosqueda of Colorado Springs, Colo., said the woman was being hoisted up the side of the stage when it appeared that she detached from her safety wire and plummeted to an open pit below the stage.

"Initially, a lot of people in the audience thought it was part of the (show)," he told the Sun. "But you could hear screaming, then groaning, and we could hear a female artist crying from the stage."

The show momentarily continued, then stopped. Minutes after the accident, a recorded announcement informed audience members that refunds or vouchers to future shows would be offered, and the crowd was dismissed.

Clark County coroner's officials say they expect to rule on the official cause of death Tuesday. Nevada officials said the Occupational Safety and Health Administration opened an investigation into the incident, and Cirque officials promised their full cooperation.

Menard said Guillot-Guyard didn't slip out of her harness, but couldn't provide additional information about what led to the deadly fall. OSHA's conclusions aren't expected for months.

Guillot-Guyard, a mother of two, had been with the original cast of "Ka" since 2006, and had been an acrobatic performer for more than 20 years, according to Cirque officials. Born in Paris, she is also listed as the head coach at Cirquefit, a program that offers acrobatic fitness classes for children.

On a memorial website in her honor, commenters thanked her for inspiring their children, recalled her "infectious laugh" and poured out their condolences in English and French.

The accident occurred while Cirque's top executives, including president Daniel Lamarre, were in Las Vegas to celebrate the premiere of "Michael Jackson One" at Mandalay Bay.

While accidents are rare -- and until now, never fatal -- they do happen. On Wednesday night, a performer in a preview of "Michael Jackson One" suffered a mild concussion after missing the protective pad below an act and landing on the stage. That artist is expected to return to the show.

"The reason there's been so few accidents is they pay so much attention to safety," said Larry Lester, who has worked in theater and previously oversaw live action shows at Universal Studios before launching an entertainment design firm. "They're constantly looking at that. They're constantly practicing."

Montreal-based Cirque du Soleil was established in 1984 and now includes more than 1,300 artists, according to its website. "Ka" is one of 20 shows playing around the world this year -- eight of which are based in Las Vegas.

"Cirque du Soleil is at the very pinnacle at these types of shows," Lester said.