A large explosion at a food-coloring plant in Louisville, Ky., on Tuesday killed two workers, according to city officials. The blast blew out the windows of nearby homes and businesses, scattered debris through the area, briefly prompted a shelter-in-place order and injured several other plant workers.

Speaking at a news conference on Wednesday, Mayor Craig Greenberg called the explosion at the Sense Colour facility “incredibly sad and tragic.” The plant produces food additives such as the caramel used in soft drinks and is owned by Givaudan, a Swiss company.

The cause of the blast is under investigation, officials said on Wednesday, adding that they did not have reason to believe there was anything nefarious at play. They also said that the air was being monitored and sprinkler runoff at the site was being tested, and that they had not found any evidence of hazardous substances.

Around two decades ago, an explosion at the same plant — which at the time was owned and operated by another company — killed one person and prompted a shelter-in-place order because of a release of ammonia solution.

Givaudan said in a statement that it was “grieving with the families” of those killed this week and cooperating with the authorities in their investigation, which will involve the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The blast on Tuesday, which took place around 3 p.m. in the Clifton neighborhood of Louisville, was heard many miles away and prompted nearly 300 calls to 911, according to emergency officials. Minutes after the first call, firefighters responded to the scene and “found an area that had obviously dealt with a tremendous explosion,” Mayor Greenberg said.