Fire crews rushed to J.P. Riddle Stadium around 10 a.m. Thursday.
Officials said when employees went to light one of the cookers in the concession area the built- up gas inside the stadium caused the blast.
A small army of police officers and firefighter responded to an initial report that a propane truck exploded. However, when fire fighters arrived, they discovered the propane from a tank next to the building had leaked.
Sources close to the investigation told ABC11 that employees had been renovating the concession stand area and had moved the propane gas cookers inside the building to repair the floor.
Investigators said when employees went to light the cookers, an explosion took place. They said a fire ball burned four people inside the building.
The four were injured and sent to the hospitall. Team manager Darrell Handelsman and team operations manager Mark Wilderman suffered severe burns and were taken to UNC Jaycee Burn Center in Chapel Hill.
J.P. Riddle Stadium is home to the Fayetteville SwampDogs - a Coastal Plain League team. The league features college players from across the nation.
The SwampDogs' home opener is still scheduled for Wednesday.