Authorities say a fire has destroyed a century-old building on a historic northern New Hampshire estate known for its conservation practices and pick-your-own Christmas tree farm.

Firefighters say the fire at the Rocks Estate in Bethlehem broke out at about 6 p.m. Wednesday. The cause is undetermined.

The fire destroyed a barn called the tool building that currently serves as an office and events center for the Society for the Protection of New Hampshire Forests. Society spokesman Jack Savage said staff members weren't hurt.

The fire also spread to two other buildings. Firefighters managed to save the property manager's home nearby.

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