Firefighters battling a huge blaze at a closed manufacturing plant in northeast Nebraska are trying to turn off the flow of propane that's fueling the fire.

There were no immediate reports of injuries from the Thursday morning blaze.

Fire officials told reporters that three crews were working to turn off the valve to a 30,000 gallon propane tank at the former Protient plant in Norfolk. Authorities have evacuated the area because they're worried the tank could explode.

Norfolk city administrator Al Roder says the tank had been filled on Wednesday.

Protient manufactured and marketed dairy-based ingredients for dairy products. It closed in October 2008.

Norfolk is a city of about 23,000 and lies 90 miles northwest of Omaha.