Dozens of people were injured when a fireworks display went awry in Simi Valley, California, Reuters reports. At first, Simi Valley police said that 28 people were hurt by the incident but calls to local hospitals suggest that at least 35 spectators were injured. According to Simi Valley polic spokesman Sergeant Tom Meyer, the accident was caused by a collapsed launching platform.

“What we understand is potentially one of the launching stations fell over, resulting in ignited fireworks going into the crowd,” Meyer said. The fireworks ignited into a crowd of 8,000 to 10,000 onlookers. Injuries include burns, shrapnel wounds, chest pain and trauma from being trampled on in the crowd.

The California Occupational Safety and Health Administration is probing the incident to further investigate exactly what went wrong. Police say that Bay Fireworks of Bethpage, New York, who mounted the fireworks show, is complying with the probe. The fireworks show was held by the Simi Valley Rotary Club. It was the Rotary Club’s second time using Bay Fireworks.

The Simi Valley Hospital

The Simi Valley Hospital received 26 patients as a result of the fireworks, according to spokeswoman Alicia Gonzalez. Gonzalez said that the patients ranged in age from 17 months to 71 years, including a dozen children. Seven people were admitted to the Los Robles Hospital & Medical Center in Thousand Oaks from the incident, according to a representative for the facility.

Accidents involving fireworks have caused chaos in the past. Reuters reports that in Seattle, illegal fireworks caused a fire at a dryland boat storage facility on Lake Union. Seattle Fire Department spokesman Kyle Moore said that as a result, 14 vessels were set on fire causing an estimated $1.4  million in damages.