An arc flash explosion at an office building in Jacksonville, Fla., sent two to the hospital with severe burns on Friday. The explosion happened in electrical equipment that powered the CSX building. One man worked for Jacksonville Energy Authority, and the other man worked for Graham & Company Real Estate, which owns the building.

They were investigating a power issue when the incident occurred in some switchgear. One man was in serious condition and the other was flown to a burn unit with life-threatening injuries.

Jacksonville Action News interviewed an instructor at the Florida Safety Council about the incident. William Burkhardt, a 35-year veteran of the construction industry, said that two lines likely became crossed inside the unit, and the flash occurred when the men opened the door.

According to actionnewsjax.com's report, Burkhardt said despite required training by OSHA, arc flash events send at least one electrician to the hospital every day in the United States. He said they are impossible to predict, and the heat can exceed 30,000 degrees, which is three times hotter than the sun. He also said figuring out what caused them is difficult.

OSHA, JEA and JSO are currently investigating.