Officials said firefighters believed they had the blaze extinguished at one point, but it flared up again.
"We had units here within about two and a half minutes. Had smoke emitting from about half of the building that you see now from the crews when they were working," explained Fire Battalion Chief Scott McGuire.
The building is a barracks for the 4th Brigade Combat Team and is under construction near the 4th Brigade barracks campus on Bastogne Street.
"We did have contractors in the building due to it under construction that were working in it at the time," said McGuire.
It's unclear how many construction workers were in the building at the time the fire was spotted, but all of them made it out safely.
Shannon Lynch, spokesperson for Womack Army Medical Center, confirmed multiple firefighter injuries.
She says five individuals were treated at Womack and two were transported to Cape Fear Medical Center for medical treatment related to heat exhaustion.
Fort Bragg says it is investigating the cause of the fire. Initial reports say the fire may have been started by a welder working near the roof.
"There were contractors in here working today that have welding capabilities and permission to do that," said McGuire. "However, I don't know if any of them were up in that area working today."
The 27,000 square foot building was scheduled to be completed by March. Military leaders say the fire has sent the project back three months.
"Well, obviously the roofing contractor is going to have to come back in. They'll finish striping off the sheathing material and the shingles and everything you see what we're doing now. And they'll have to kind of just replace everything that's on that," said McGuire.