YELLOWSTONE NATIONAL PARK, Mont. — Authorities say there's a "significant development" in the search for two convicted killers who escaped from an Arizona prison and their suspected accomplice in the Yellowstone National Park area.
The U.S. Marshals Office and Arizona authorities plan to make an announcement about the case Monday morning in Phoenix.
More than 100 armed park rangers and federal agents searched in and around tourist-packed Yellowstone, as an estimated 30,000 people entering the park were warned about the search.
Efforts to find the trio have intensified after they were linked to a double homicide in New Mexico. Rangers patrolled campgrounds on the sprawling 3,472-square-mile park that spans Montana and Wyoming.
Park employees are asking tourists they meet to be on the lookout for inmates Tracy Province and John McCluskey, as well as suspected accomplice Casslyn Welch.
There will be, however, some campers tucked deep in the rugged wilderness who will likely be unaware of the manhunt.
"They just don't have any regular access to any news because of the remote nature of the place," park spokesman Al Nash said. "The bottom line is, it's safe, everything's open and park visitors should not be unduly concerned."
The U.S. Marshals Service believes Province has separated from McCluskey and Welch. Authorities don't believe any of them have wilderness survival skills, so it's possible they could be staying in campgrounds and at truck stops.
"They are very dangerous individuals, very desperate individuals, and the longer they're out there, the more desperate they become," said Thomas Henman, supervisory deputy with the U.S. Marshals Service in Phoenix, on Sunday.
An estimated 30,000 people will enter the park on Monday, Nash said. The park has 1,800 campsites and 2,150 hotel rooms that were mostly full last night. "So that makes it a really big and busy place," he said.
Last week, the park announced a record 957,000 people visited the world's first national park in July, putting it on track to meet or exceed last year's record of nearly 3.3 million visitors. July is the busiest month, followed by August.
Province, McCluskey and Daniel Renwick escaped from a private, medium-security Arizona State Prison near Kingman on July 30 after authorities say the 44-year-old Welch threw wire cutters over the perimeter fence. Welch is McCluskey's fiancee and cousin.
The three later kidnapped two semi-truck drivers at gunpoint and used the big rig to get away, authorities said. The group left the drivers unharmed in the truck at a stop just off Interstate 40 in Flagstaff and then fled. Renwick was arrested Aug. 1 in Colorado.
The manhunt intensified Saturday after forensic evidence linked the two inmates and Welsh to the killings of an Oklahoma couple. 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 Wednesday morning on a remote ranch in eastern New Mexico. Their pickup truck was found later 100 miles west in Albuquerque.
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.
Renwick had been serving a 22-year sentence for second-degree murder.
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Publicizing their photographs in newspapers and on television, including a segment Saturday night on "America's Most Wanted," has helped generate tips, investigators said. A series of billboards featuring the three are also planned.