Authorities are still investigating the exact cause of the Butternut brush fire in the Berkshires, but fire officials say it was caused by human activity.

It may be challenging to pinpoint exactly how it started due to the size of the fire among other factors, NewsChannel 13’s media partners at The Berkshire Eagle reported.

There’s no evidence of a campfire or any ignition source, Great Barrington’s fire chief said.

It’s not clear what kind of activity caused the fire, nor whether it was intentional.

The wildfire burned more than 1,600 acres near Great Barrington in November.

Firefighters removed vegetation and dead leaves to help stop the fire from spreading. The rain and snow then helped put out hot spots, the paper reported.