LOUISVILLE, Ky. (AP) — At least 11 employees were taken to the hospital after an explosion Tuesday at a Louisville, Ky., factory caused a partial collapse of the building and blew out windows of homes and neighboring businesses.

The explosion occurred around 3 p.m. at Givaudan Sense Color, which produces colorings for food and drinks. Firefighters rescued and evacuated numerous people from the building, some of whom were seriously injured, Louisville Mayor Craig Greenberg said in a statement Tuesday evening.

Greenberg said officials accounted for everyone who worked at the plant at the time.

The cause was under investigation. Greenberg said officials spoke to employees inside the plant and they “initially indicated everything was normal when the explosion occurred.”

Patrick Livers lives in a neighborhood right across the street from the factory, across the railroad tracks. He was at work when his mother, who was picking up her children from school and taking them home, called him to tell him that her house had been damaged in the explosion.

“I was like, ‘What are you talking about? Then she showed me the video. I was like, ‘Oh, you’ve got to be kidding me,'” he said.

Livers said no one was home at the time. He said the explosion blew out windows on his street.

“The house is still standing. This is just structural damage. If it was on a wall, it’s on the floor,” he said. “All the neighbors’ windows were shattered, the doors were broken in. It looked like a small tornado had started inside the house.”

Steve Parobek was at work when the explosion blew out the kitchen window of his apartment a block from the factory. He arrived home to find his cat safe and used two pizza boxes and duct tape to cover his window as temperatures steadily dropped Tuesday evening.

A Givaudan spokesperson did not immediately respond to an email seeking comment Tuesday evening. No one answered the phone at the company’s Louisville office, and a man who answered the Port Washington, Wis., office declined to comment.

University of Louisville Hospital treated seven of the injured and two were in critical condition, said Dr. Jason Smith, University of Louisville Health chief medical officer. Hospital officials activated decontamination procedures for the victims, a process that involves removing their clothing and any chemicals contained in them, then taking them for evaluation and treatment, Smith said.

Louisville Fire Chief Brian O’Neill said air monitoring began immediately after the explosion and “nothing at this point has ever shown any chemical problem in the air in any this region. O’Neill also said firefighters “don’t yet know exactly what types of leaks might be occurring or might be in progress,” but he urged residents to remain calm.

The Louisville Fire Department was leading the investigation Tuesday evening with assistance from state and federal partners. A reconstruction team from the Bureau of Alcohol, Tobacco, Firearms and Explosives traveled to Louisville to help determine the cause of the explosion.

In April 2003, an explosion at the same location killed an employee at a caramel coloring factory owned by DD Williamson & Co. Givaudan acquired the factory from DD Williamson in 2021.

Federal investigators determined that a pressure relief valve on a tank was removed when the company moved the tank to its Louisville plant in 1989. The tank exploded because there was no pressure relief valve , according to a report from the Chemical Safety Board.

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Associated Press journalists John Raby and Bruce Schreiner contributed to this report.