WINDHAM — The Environmental Protection Agency has added a former mill site in Windham to the Superfund list of hazardous waste sites.

Since the 1750s, the Keddy Mill Site has been a saw mill, gristmill and wool carding mill as well as a wood pulp facility. It has also been used to manufacture boxboard, steel, heavy equipment buckets and fire suppression piping and materials.

It closed in 1997 and several buildings have been demolished.

The property is known to be contaminated with polychlorinated biphenyls, or PCBs, which is suspected of causing cancer.

Superfund investigates and cleans up the nation’s most complex, uncontrolled or abandoned hazardous waste sites.

About 10 tons of contaminated soil has already been removed from the site and a fence has gone up to deter trespassers.