BLOOMING GROVE TWP. – State police said they found two pipe bombs they believe were left behind by suspected police killer Eric Matthew Frein.

The functional pipe bombs - which could have been activated by being lit or via trip-wire - were found within the past 24 hours in the search area, state police Lt. Col. George Bivens said Tuesday at a news conference during the 18th day of the search for the 31-year-old Canadensis man.

The bombs were loaded with shrapnel such as nuts and bolts and aimed at causing a maximum amount of damage, Bivens said.

The explosives are being examined by the FBI.

Bivens said he believes Frein is "clearly stressed" and is making "significant mistakes."

The explosives were not intentionally left behind, but it appeared they were abandoned in haste, Bevins said.

Police said the approximate five-square-mile search perimeter has shifted somewhat south but remains in the border of Pike and Monroe counties.

Frein is accused of fatally shooting state police Cpl. Bryon Dickson II, 38, outside the barracks in Blooming Grove Township on Sept. 12. Trooper Alex Douglass, 31, also was shot but is recovering and could soon be out of the hospital.

Anyone who has any information is urged to call tip line 1-866-326-7256.

Pike County District Attorney Ray Tonkin said the discovery of the explosives reinforces the fact that trackers have to be methodical and vigilant in the search.

Bivens said that, within the past 24 hours, there has been credible sightings of Frein in the Barrett and Price townships area of Monroe County. But "unfortunately he's managed to escape" due to the rough terrain and other factors.

"It is not an easy thing to set up a secure perimeter," Bivens said, noting the sightings happened between 75 and 100 yards in a thick, wooded area.

Bivens said trackers have been searching hundreds of cabins and vacant homes within the perimeter.

The officer also reiterated that authorities believe Frein is not being aided and he did not specifically target the two troopers who were shot.

Frein is believed to have a longstanding grudge against law enforcement.

Bivens said authorities are trying to lessen road closures to accommodate residents in the area.

The manhunt may impact hunting season.

The Northeast Region Office of the Pennsylvania Game Commission advises hunters to anticipate police presence in parts of Monroe and Pike counties and to plan accordingly.

The statewide archery deer season starts Saturday, Oct. 4, and many hunters take to the woods prior to the opening day in order to scout for deer and place tree stands.

Areas of potential continuing police activity include Price, Barrett and Paradise townships in Monroe County, and Blooming Grove, Porter, and Lehman townships in Pike County.

“Hunters should use common sense and good judgment until this situation is resolved,” Game Commission Northeast Region Director Daniel Figured said in a release. “Our advice is to avoid wooded areas with obvious police activity and use extreme caution when afield, especially in Monroe and Pike counties.”

State police and the Game Commission are not currently restricting hunting activity in the area of the manhunt, but hunters should anticipate encountering law-enforcement personnel conducting search operations.

“It is imperative that hunters do not interfere with the search operation,” Figured said.

The Game Commission "strongly recommends" hunters wear fluorescent orange material whether moving or in a stationary position.

“To avoid potential misidentification, make it obvious that you are a hunter,” Figured said.

Hunters who come upon cabin entrances that appear to have been tampered with should call 911 and not disturb any potential evidence, Bivens said.