Two firefighters were taken to the hospital after battling a five-alarm fire Tuesday night at the PepsiCo factory in Piscataway.

Fire crews are still working to figure out what exactly started the fire, but they do know it began outside the back of the building.

"That's where the fire started and climbed up the side of the wall that actually got in the membrane - that's where parts of the building collapsed in the back,” says Mayor Brian Wahler.

The fire broke out just after 6 p.m. outside the factory on New Brunswick Avenue. The fire sent large plumes of black smoke into the sky, which could be seen for miles.

Bright orange flames were also seen on the roof of the building. One witness described the scene as a “tornado of fire.” Others reported hearing loud explosions from miles away.

Officials say all PepsiCo employees were safely evacuated. The plant manager says the staff trains for emergencies like this on a regular basis. No employees were hurt. Michael Coyle stopped to take video.

"It was huge,” says Coyle. "The flames were so high. We were worried about the other tanks catching fire. People were nervous. Everybody was running around."

More than 100 firefighters from Piscataway and surrounding towns came to battle the fire. One volunteer firefighter was taken to the hospital to be treated for heat exhaustion. Another suffered a shoulder injury. Both are expected to be OK.

"It could've been a lot worse, and I want to give kudos to all of those volunteer firefighters who were out there last night,” says Wahler.

A small brush fire was put out early on. The state Forest Fire Service is also on scene.

The mayor says the factory usually open 24/7, but it is unclear when it will reopen.