A Rural Fire Service spokesperson has confirmed that the Louth Park shed fire was caused by spontaneous combustion of hay.

Fire crews were called out to the Ross Lane shed about 8.30pm Thursday.

RFS crews from East Maitland, Mulbring, Bolwarra and Thornton attended, along with a Lower Hunter support crew.

Fire and Rescue brigades from Maitland and East Maitland also assisted on scene.

It took about three and a half hours to put out the blaze.

Two hours alone was spent on the hay bales, which had to be removed from the shed, broken apart and extinguished.

The fire caused no threat to homes, people or animals.

INITIAL REPORT

Five fire crews attended a major shed fire at Louth Park on Thursday night.

The Mercury understands the fire, at Ross Lane in Louth Park, was caused by mulch combusting.

Crews from East Maitland, Mulbring and Thornton Rural Fire Service attended the blaze.

East Maitland and Rutherford Fire and Rescue NSW also visited the scene.