A stubborn fire in a silo at a pet food processing plant in Hazle Township kept firefighters from four counties busy Tuesday night into Wednesday as they meticulously worked to extinguish the smoldering product and contain damage.

Bill Gallagher, Hazle Township supervisor and volunteer firefighter with its fire company, was one of many who responded to Vita Line, in the Humboldt Industrial Park, when the fire began Tuesday around 6:30 p.m.The business is a short distance from Route 924. Firefighters at first believed equipment inside the plant caught fire and later sparked two secondary fires.They just about had the blaze extinguished around 9 p.m., Gallagher said, when Vita Line maintenance workers found two other pieces of equipment on fire, including a silo. After the discovery of the new fires, Hazle Township Fire and Rescue contacted Luzerne County 911 and requested additional fire companies to respond with more manpower, Gallagher said.Espy Fire Company from the Bloomsburg area was dispatched as they have expertise in handling silo fires, as well as the state Department of Environmental Protection and Luzerne County and Hazle Township emergency management officials.At 3 p.m. Wednesday, while firefighters were in their 21st hour of tackling the blaze, Gallagher said silo fires have to be approached with caution. He said if water from a hose is placed on the fire inside the silo, the steam could be so great that the silo would split. Also, silos storing any type of product that creates dust can cause the silo to explode due to heat building up inside it.If oxygen is added to the silo, he added, it can create a "fire vacuum," causing the dust to become combustible.The exact cause of the fire has not been determined. However, at about 3:30 p.m., Gallagher said, there was a flare-up in the silo caused by a dust explosion. No major injuries were reported initially, but 23 firefighters in the basement during the explosion were examined by medical personnel from ambulance companies, he said.Volunteer firefighters rotated shifts at the plant to prevent exhaustion and to allow those who had worked during the fire to leave, resulting in multiple crews from companies in Luzerne, Carbon, Schuylkill and Columbia counties responding to the scene.