Despite the tightened security, there are many backroads and other ways for Arizona escapee John McCluskey and his suspected accomplice, Casslyn Welch, to slip across the border and into Canada, Glacier County Undersheriff Jeff Fauque said.
"There are no border sensors, no border patrolmen or (Royal Canadian Mounted Police) officers around," Fauque said. "It's definitely possible for somebody to enter Canada undetected."
Authorities at Montana border crossings have started checking cars headed into Canada, scanning the faces of the occupants to see whether they match the description of the fugitives, who apparently have dyed their hair to try to disguise themselves.
"We're doing outbound checks at ports of entry to ensure any fugitive is unable to utilize that avenue of escape," U.S. Customs and Border Patrol spokesman Mike Milne said late Tuesday.
A U.S. Border Patrol helicopter joined the search Tuesday, but authorities on both sides of the border acknowledged it was impossible to completely secure it.
Glacier National Park abuts the Canadian border in rugged terrain, but the border to the east, along the Blackfeet Indian Reservation, is fairly flat. Fauque said there are several small roads that cross the border.
Sgt. Patrick Webb, a spokesman for the Royal Canadian Mounted Police in Calgary, Alberta, said Wednesday morning that Mounties do not believe the pair has entered Canada.
"We've got no physical evidence or sightings to confirm that they're here," Webb said.
Fidencio Rivera, chief deputy U.S. marshal for the Arizona district, told The Associated Press Wednesday the two apparently have changed their appearance.
"Welch has dyed her hair blond, McCluskey has dyed his hair black," Rivera said.
The information was developed through interviews with people who last saw the couple, Rivera said.
The last confirmed sighting of McCluskey and Welch together was Friday in Billings, Mont., and that wasn't confirmed until Monday.
U.S. marshals said there have been reports that Welch was spotted Sunday at a restaurant in St. Mary east Glacier National Park. Montana's acting marshal, Rod Ostermiller, said there were multiple other tips from the Glacier area, but he didn't say whether any included sightings of McCluskey.
Ten miles north of St. Mary, residents of Babb have been frightened by the presence of police cars patrolling the streets. The town of 700 normally sees a patrol car every other week, said Tedi Burns, a bartender at the Babb Bar Cattle Baron Supper Club.
"This is a small town and nobody can find them," said Burns, 19. "They could be hiding in the woods. We have mountains around us. We have a bunch of backwoods they could be hiding around."
Another prisoner who escaped with McCluskey was due in a Glenwood Springs, Colo., courtroom Wednesday morning. Daniel Renwick, who was serving a 22-year sentence for second-degree murder, was captured Aug. 1 in western Colorado.
A day earlier, the third escapee, Tracy Province, appeared in a Cody, Wyo., court and waived his right to fight extradition to Arizona. Province was caught Monday as he walked in sleepy Meeteetse, Wyo., steps from a church where he sat in the pews a day earlier and sang "Your Grace Is Enough."
Province, McCluskey and Renwick escaped from the medium-security Arizona State Prison near Kingman on July 30 after authorities say Welch threw wire cutters over the perimeter fence. Welch, 44, is McCluskey's fiancee and cousin.
Province was serving a life sentence for murder and robbery out of Pima County, Ariz. McCluskey was serving a 15-year prison term for attempted second-degree murder, aggravated assault and discharge of a firearm out of Maricopa County, Ariz.
The Arizona attorney general's office on Monday charged McCluskey's mother and ex-wife with helping the inmates after they escaped.
Forensic evidence linked the escapees to the killings of an Oklahoma couple in New Mexico. New Mexico State Police spokesman Peter Olson declined to elaborate.
The badly burned skeletal remains of Linda and Gary Haas - both 61 and from Tecumseh, Okla. - were found in a charred camper last Wednesday on a remote ranch in eastern New Mexico. Their pickup truck was found later 100 miles west in Albuquerque.