Police, EMS and fire crews surrounded the scene of an explosion at 1901 Payne Street in Louisville. Several people were transported to the hospital with injuries.(Roberto Roldan / LPM )Around 3 p.m. Tuesday, an explosion at Givaudan Sense Colour in Louisville sent dozens of workers fleeing from the plant. The factory at 1901 Payne Street produces colorings for sodas and foods. First responders transported 11 workers to the hospital. One person was pinned inside the building and had to be rescued.The cause of the explosion was still unknown Tuesday afternoon, but the factory sustained massive structural damage, and some nearby homes and businesses had their windows blown out. Two people who lived at the Axis on Lexington Apartments, about a third of a mile away, said they felt the building shake.At a press conference near the plant, Mayor Craig Greenberg said air monitoring showed no signs that the explosion released toxic chemicals into the air.“We’re working to get more details from the company so we can have more information on what was inside the facility, what chemicals may have been involved,” Greenberg said. “We don’t have that information at this time.”City officials warned anyone within a two-mile radius to shelter-in-place during the immediate aftermath of the explosion. By 4:30 p.m., the shelter-in-place order had been lifted but residents living within two blocks of the Givaudan plant were still being asked not to return to their homes. The blast at 1901 Payne Street shattered windows at Quills Coffee on Frankfort Avenue.(Tracy Karem / LPM)One man on a sales trip from Cincinnati, who did not want to be named, said he was inside the plant when the explosion occurred. The man said he left the building after hearing a loud boom. He said he saw at least one person come out of the plant on a stretcher, covered in what appeared to be molasses or coloring agent.Another man said he was parked in his truck just outside of the factory gates when the explosion happened. He said material from the plant flew into his truck, leaving a large hole in his windshield. He also did not want to be identified.This is the second explosion that occurred at this facility. In 2003, a vessel inside the factory exploded, leading to what officials said was a “massive release of aqua ammonia.” One person was killed in that incident.A 2004 analysis of the U.S. Chemical Safety and Hazard Investigation Board found the root causes of the factory explosion, then owned by D. D. Williamson & Co., Inc., were a lack of training and safety procedures.Louisville Fire Department Chief Brian O'Neill said Wednesday this second explosion will be under investigation “for some time” and it will be a while before any cause is determined.Residents are being asked to avoid the area surrounding the 1900 block of Payne Street while emergency services continue their work.