PENNSYLVANIA (CNN) -- Area schools were closed Tuesday as the search for Pennsylvania trooper shooting suspect Eric Matthew Frein intensified overnight, Pennsylvania State Police said.
Despite a possible sighting by law enforcement Monday afternoon, Frein still has not been found.
"A local police officer from Pocono Mountain Regional Police Department observed a man dressed in green in the woods. He lost visual contact with the man through the woods. A search of the area was conducted but no one was located," state police said.
It has been nearly six weeks since Frein disappeared after allegedly shooting two state troopers, leaving one officer dead and another wounded.
On Friday, state police discovered blood droplets on the steps of a covered porch near the town of Cresco, Pennsylvania. But DNA testing showed the blood wasn't Frein's, police said Monday.
Material found on the inside of a screen porch door at a nearby home wasn't blood at all, police said.
Neither has any link to the search for Frein, according to police.
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 his.
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 in northeast Pennsylvania.
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.
He has eluded capture despite a massive police search around Canadensis, Pennsylvania, where his family has a home. However, another recent sighting moved search efforts about 8 miles southeast -- closer to Frein's former high school.
Police say they think a woman taking a walk Friday night saw Frein as well, armed with a rifle and his face dabbed with mud, in a wooded area near the eastern Pennsylvania town of Swiftwater.
"It was very alarming and creepy how he showed no reaction," the woman told CNN affiliate WNEP.