Authorities are releasing new information in the search for an escaped Arizona inmate and his female accomplice, hoping the public will spot the fugitives as they step up search efforts in the northwestern U.S. and Canada

The last credible sighting of Casslyn Welch and John McCluskey was on Aug. 6 in Billings, Mont., and the couple is believed to be traveling in a sliver or gray 1997 Nissan Sentra sedan.

McCluskey was serving a 15-year sentence for attempted second-degree murder and other crimes when he escaped from the Arizona State Prison in Kingman on July 30, along with two other inmates who were later captured. 

Welch, McCluskey's fiancee and cousin, is accused of throwing wire cutters over a perimeter fence that the men used to slice their way out and flee. 

Welch's visitation privileges at the prison were terminated after a random search in June during a visit to McCluskey turned up what was believed to be heroin. Welch told investigators that she was paid by members or associates of a white supremacist group to smuggle the drug into the prison but didn't say who it was intended for.

On Wednesday, the Arizona State Prison Kingman Escapees Task Force released new information on the couple's appearance to aid in the search.

McCluskey is missing an upper left tooth and Welch is missing almost half of her right index finger. Authorities said that Welch smokes by holding the cigarette between her right middle and right ring fingers.

The U.S. Marshals Service is asking travelers at truck stops and in campgrounds nationwide to watch out for the couple, who may have dyed their hair and otherwise changed their appearance. McCluskey may have dyed his hair dark and grown a beard, authorities said, and Welch may have blond hair. Both are experienced long-haul truckers and McCluskey "may have some survival skills, giving him the ability to live off the land," authorities said.

Investigators said the 1997 Nissan Sentra sedan that the two are believed to be traveling in originally bore Arizona license plate 620 PFV but may have been switched to another plate. 

"All information indicates McCluskey and Welch continue to travel together and should be considered armed and extremely dangerous. As the manhunt continues, it is highly possible they will become more desperate, creating increased danger to law enforcement and
the general public," the task force said in a news release on Wednesday. 

Investigative efforts in recent days have focused in Arkansas, where Welch has family, and Montana, where the two were last seen Aug. 6. The two are considered among the most wanted fugitives in America and are financing their getaway by committing crimes along the way and using their experience as long-haul truck drivers, authorities said. 

A reward of up to $35,000 is being offered for information leading to their arrest. 

Welch is facing a growing list of charges since the escape that include kidnapping, armed robbery and aggravated assault.

On the night of the prison break, Welch had allegedly packed a getaway car nearby with cash, weapons and false identification. Renwick, Province and McCluskey became disoriented and could not find the car after they cut through the prison fence.

The group split up, and Renwick found the vehicle and drove off, leaving the other three to hijack a tractor-trailer and head to Flagstaff. Renwick, who was serving time for second-degree murder, was arrested after a shootout with law enforcement in Rifle, Colo., two days after the escape.

The rest of the group was linked through forensic evidence to the deaths of an Oklahoma couple whose bodies were found in their charred camper in eastern New Mexico last week, authorities there said.

Province, who was serving a life sentence for murder and robbery, was captured without incident after being spotted hanging out and singing hymns at a Wyoming church.

The Associated Press contributed to this report