A two-alarm blaze caused $200,000 damage to a huge barn full of hay at Star Rock Farms in Manor Township, fire officials said.

It is the second barn fire in the last four years at the 175 Chestnut Grove Road farm, one of the county's largest dairy farms.

The latest blaze started shortly before 11 p.m. Tuesday and continued to burn throughout the day Wednesday.

"The barn is roughly the size of a football field," Mike Ditzler, fire chief of Highville Fire Company, said Wednesday. "The hay is packed in there really tight, and we are trying to let it burn on its own."

Ditzler did not predict how long the fire would burn.

Robert Barley, a Star Rock Farms partner and son of former state Rep. John Barley, said Wednesday that the fire could burn itself out sometime today.

No people or animals were injured in the fire, Ditzler said.

The barn was 50 feet by 300 feet and was 30 feet high. The 1,000 tons of hay inside the barn, valued at $120,000, and the $80,000 building itself were destroyed in the blaze, he said.

"There was no electricity in the barn and no cause for anything suspicious, so the fire was probably spontaneous combustion due to hot hay," Ditzler said. Outside temperatures in the 90s combined with heat released by the aging of the hay must have been enough to spark a blaze.

But Robert Barley said he was "very baffled" by the fire.

"We did not have wet hay," he said. "We had good weather (when the hay was harvested). Some years, it is a challenge, but this year it hasn't been."

Also, spontaneous combustion in hay usually occurs within two to three weeks after harvest, Barley said. Hay was last put in the barn more than a month ago.

The large square hay bales were to feed about 1,200 cows at Star Rock Farms, he said. Replacement hay will have to be bought.

A deliveryman took grain to the farm at 10:30 p.m. Tuesday and did not see any fire, Ditzler said.

A short time later, workers at the farm's nearby dairy barn heard a pop or bang, he said. Flames consumed the entire hay barn a few minutes later.

Sixty-five firefighters from about a dozen area fire companies responded to the fire, originally reported to be a brush fire, Ditzler said.

Trying to extinguish the fire likely would have caused it to keep re-igniting, and the water used could have caused runoff problems, Ditzler said.

So firefighters instead worked to contain the fire, he said. They prevented the flames from reaching farm implements and tractor-trailers outside the barn or the adjoining woods.

The barn was built in the last two years to replace a smaller hay barn destroyed by a fire in 2006, Ditzler said.

That fire also likely was caused by spontaneous combustion from hay, Barley said at the time.

rrobinson@lnpnews.com