The entire western edge of the massive wildfire burning north of Los Angeles was under control Saturday, but the arson-caused blaze continued to move unchecked into wilderness to the east, AP quoted officials as saying. Investigators, meanwhile, were working to find the arsonist responsible for the huge wildfire that has killed two firefighters and burned nearly 242 square miles (630 sq. kilometers) of the Angeles National Forest. It was 49 percent contained. At least 76 homes and dozens of other structures have been destroyed. Gov. Arnold Schwarzenegger offered a $100,000 reward for information leading to the arrest and conviction of the culprit. The risk to homes was significantly reduced as hand crews held the fire line to the north, south and west, said U.S. Forest Service spokeswoman Michelle Caldwell. Aerial water drops were expected to resume Saturday to slow the fire's eastern movement into the rural San Gabriel Wilderness. Overnight, firefighters built six miles (10 kilometers) of new lines on the northwestern flank of the blaze near Santa Clarita, according to Forest Service spokeswoman Barbara Rebisky. The weekend weather forecast called for cooler temperatures and slightly higher humidity that could help firefighters further surround the blaze, which has cost fire agencies $37 million to fight. At least a dozen investigators were working to analyze clues found at a charred hillside, including incendiary material reported to have been found there. Officials said the fire was arson but were still investigating who started it and how.