The fire was reported around 7:30 a.m. at the Case Pork Roll Company facility, located at 644 Washington Street in the Chambersburg section of the city.
Investigators say the fire started in a machine used to smoke meat. Workers had begun their shift and noticed something was wrong.
"We were pushing down some of the meat into the oven and we noticed there was some extra smoke coming down," said employee Drew Grieb.
A fire erupted and spread to the roof.
Workers called 911 and everyone was evacuated safely.
It took firefighters about two hours to bring the flames under control. Most of the building was saved.
Owners are hopeful to have the roof, smoker machines and duct work replaced and be back in operation in a few weeks.
The company has about two dozen employees.
Owned by the Grieb family, Case's has been making its old-fashioned, hickory-smoked pork roll - nicknamed Jersey ham - since 1870.