Brush fires on the Blue Mountain in Lehigh Township were intentionally set.

Investigators from the Department of Conservation and Natural Resources have ruled the large and smoky wildfire that broke out just before 2 p.m. May 1 as arson.

However, authorities have not determined what set off the two fires, one that spanned over 15 acres and a smaller one that covered just a quarter of an acre.

Crews from close to 20 emergency response agencies responded and resulted in the shutdown of Route 248 in both directions between Lehigh Gap and Berlinsville.

Fire was reported at 1:53 p.m., and within minutes, crews began arriving.

Firefighters battled the flames from the ground and from the sky. Some fought by foot, while others used UTVs to access flames on the rocky and steep slopes.

Emergency response vehicles from three counties lined both lanes of a closed portion of Route 248, while others accessed the fire from the Appalachian Trail parking lot, just off 248.

A helicopter contracted by the Bureau of Forestry helped snuff the flames with its large bucket filled with water from the nearby Lehigh River, and dropped it on the hot spots.

By 6 p.m., most of the flames had been extinguished.

DCRN spokesperson Wesley Robinson noted that 99% of wildfires in Pennsylvania are started by people.

“We encourage people to be smart and respectful of the rules,” Robinson said. “We want to make sure the people follow the guidelines.”