Firefighters from surrounding communities spent much of Thursday battling a fire at a Mercer County barn.

Crews were first called to the David Yoder farm in New Vernon Township just before 11 a.m. when flames broke out in a two story barn filled with hay.

Fire officials tell 21 News they believe that hay inside the barn burst into flame due to spontaneous combustion.

A second alarm was called in for more equipment and manpower to help remove some of the hay from the barn.

Investigators say they managed to keep the flames from spreading from the hay to the barn itself.

One firefighter was treated on the scene for heat exhaustion.