(CNN) -- A man suspected of killing a Pennsylvania state trooper might have been spotted near his former high school, police said Saturday -- a potential boost for authorities' weekslong and multimillion-dollar quest to find him in the woods.
Investigators believe a woman saw Eric Matthew Frein in a wooded area near the eastern Pennsylvania town of Swiftwater on Friday night, State Police Lt. Col. George Bivens told reporters.
The woman was taking a walk when she saw a man with a rifle, his face obscured by mud, just off a road near Pocono Mountain East High School just after 9 p.m., Bivens said.
She couldn't identify him because of the mud, but investigators' minds went to Frein, who police say is a survivalist who has been hiding in the sylvan Pocono Mountains in the weeks since the slaying.
Frein is familiar with the Swiftwater area, having attended the high school and having worked summers at a camp just to the west, Bivens said.
"Our investigators believe this was likely Frein," Bivens said at a news conference in Barrett Township.
If Frein was in Swiftwater, he was about eight miles southeast of where authorities have been heavily searching -- the Canadensis area, where his family has a home.
Frein, 31, is suspected in the September 12 ambush shooting that left Cpl. Bryon Dickson dead and Trooper Alex T. Douglass wounded outside the Pennsylvania State Police barracks in Blooming Grove, about 25 miles northeast of Sweetwater.
A massive search for Frein has been carried out since, at times involving as many as 1,000 officers, some from other states. Despite recent sightings and other leads -- including handwritten notes attributed to him left in the woods -- he has eluded authorities. The manhunt has cost several million dollars, Bivens said.
Police have not spoken about a possible motive, other than that Frein has talked and written about hating law enforcement. Authorities have said that a review of a computer hard drive used by Frein shows that he had planned the attack for years.
Bivens said Frein also might have been sighted south of the Canadensis area earlier this week. He did not elaborate, but he added that Frein hasn't been spotted in or immediately near Canadensis "for the past week."
Police testing whether porch 'blood' linked to case
Bivens told reporters that police are investigating whether a blood-like substance found on the back porches of two homes in the town of Cresco, between Swiftwater and Canadensis, has any connection to the case.
Testing has determined that one of the substances is blood, but Bivens didn't say whose it was, adding that more tests are pending. Results on the other collection also weren't back, Bivens said.
Asked whether authorities believed Frein was injured, Bivens said that they would have a better idea once testing is complete. Investigators are working on an assumption that Frein is mobile.
On Friday, a law enforcement source speaking on condition of anonymity told CNN that there was no reason to believe that Frein was injured, or that the blood was Frein's.
As for Friday's sighting, it was near the high school but not on the school's property, Bivens said. He said police weren't recommending that the school cancel classes.
CNN's Ray Sanchez contributed to this report.