One hundred pigs died in a fire in a Waikato piggery last night.

The pigs died in a blaze which destroyed the main building at the Hopuhopu operation, north of Ngaruawahia.

Fire Service northern shift manager manager Scott Osmond said motorists on State Highway 1 raised the alarm about 8.20pm after flames were seen coming from the farm.

Five fire trucks raced to the scene at the former military camp and managed to stop the fire from spreading to other buildings.

"Only one building was damaged but it was quite large," he said. "We've been advised sadly that 100 pigs were killed in the fire."

He said there was smoke damage to adjoining buildings where other pigs were housed.

A special appliance was travelling to the scene from Hamilton with a large fan to clear the smoke from neighbouring buildings.

Fire investigators were on their way to determine the cause of the blaze.

About 300 pigs perished in a blaze that broke out in the piggery's breeding area 10 years ago.