Stairway collapse injures 21 children, 2 adults at parkour gym in San Diego

— -- A stairway collapse at a crowded San Diego parkour facility injured 21 children and two adults on Saturday evening.

According to the San Diego Fire Department, the injuries were considered minor to moderate.

The collapse happened just after 8 p.m. PT at Vault PK when a large group of kids climbed up on a platform and the whole structure collapsed, injuring those on the platform and underneath it, according to San Diego ABC affiliate KGTV.

Cory Brizendine, a parent, told KGTV there were about 50 kids there at the time, and they were called up to the platform for pizza.

"Once the majority of kids got up there the whole platform collapsed," he said.

One of the injured adults was a 72-year-old woman and the other was 46 years old. Neither were employees, according to authorities.

One child possibly suffered a moderate spinal cord injury due to the way he fell and a second child suffered a possible moderate head injury, the San Diego Fire Department said.

Vault PK owner and founder Jessica Ho issued a statement about the accident, saying she was "devastated."

"We are truly heartbroken tonight, as these children and their parents aren’t just our members -- we see them weekly, they are our gym family," Ho said. "I had my own children there tonight. I am just as devastated for all the children affected as any other parent. Their safety has always been a priority. My heart aches for the families who call Vault PK home.

"We are working with authorities and will continue to do so to resolve this," the statement continued. "That is all we can say for now."

The parkour facility is located in a large warehouse in the Barrio Logan section of the city.

Parkour is a physical discipline in which participants attempt to get from one point to another, often involving jumping from one structure to another at obstacle course-like facilities. Developed in France, the discipline has gained popularity in the U.S. through media such as the "Assassin's Creed" video game series and TV show "American Ninja Warrior."