The 30-story-tall crane collapsed at the refinery located in southeast Houston at 2 p.m., said Jim Roecker, vice president of the refinery.
The workers were in the area of the crane, but officials are unsure if they were on or beneath the crane at the time of the accident.
Three workers were treated at the accident scene. Two workers suffered serious injuries and were transported by helicopter to Memorial Hermann-Texas Medical Center and the other two workers were taken by ambulance to the hospital, according to Assistant Chief of the Houston Fire Department.
Deep South Crane & Rigging, the crane owners, are known as one of the nation’s largest mobile crane operators with equipment 300 feet tall.
Officials are unsure what caused the crane to collapse. Refinery officials are hopeful that one of the many security cameras in the area captured video that will assist officials in figuring out what caused the accident, so this type of tragedy does not happen again in the future.