The founder of Cirque du Soleil says his performance company is "completely devastated" after an acrobat fell to her death over the weekend, with the audience watching.

It was the first stage casualty in the company's 29-year history, according to Cirque spokeswoman Renee-Claude Menard.

Coroner's officials said French-born Sarah Guillot-Guyard, 31, was pronounced dead at a Las Vegas hospital late Saturday after falling about 15 metres from the stage during a production of Ka. The show has been suspended.

"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."

Witnesses told the Las Vegas Sun newspaper that the accident occurred during a fight scene near the end of the production, which combines acrobatics with martial arts and puppetry and tells the story of twins on a heroic quest.

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

"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, the crowd was dismissed.

Clark County coroner's officials say they expect to rule on the official cause of death Tuesday.

Menard said she could confirm that Guillot-Guyard didn't slip out of her harness, but she couldn't provide additional information about the incident.

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.

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.