The flames were reported at about 7:40 p.m. Monday, and witnesses at first weren't sure whether it was in Lehigh, Carbon or Northampton county.
Officials later were told that it was between the Lehigh River and the Blue Mountain Ski Area, about 15 miles north of Allentown.
A Northampton County emergency official told The Morning Call an hour and a half later that the fire was not totally contained but was no longer burning out of control.
Fire officials reported finding a campfire that appeared to have been abandoned hurriedly. They said the blaze appeared to be fueled more by grasses than by trees.
