Latest in search for man accused of killing 3 young daughters

Authorities released a new suspect flyer Tuesday amid the manhunt for Travis Decker, the father accused of murdering his three young daughters near a Washington campground last month.

Decker, an Army veteran, is wanted for three counts of first-degree murder and three counts of first-degree kidnapping, police said.

His daughters -- Paityn Decker, 9; Evelyn Decker, 8; and Olivia Decker, 5 -- had left home for a "planned visitation" with him on May 30, officials said. Three days later, the girls were found dead near the Rock Island Campground in Chelan County, Washington, following a search, police said.

Decker's truck was recovered at the scene, but he was nowhere to be found.

Amid the search, the Chelan County Sheriff's Office released a new suspect flyer including photos of potential ways Decker may have altered his appearance in the weeks since he was last seen.

Decker is considered dangerous and may be armed, the sheriff's office warned.

The U.S. Marshals Service, which is leading the search for the suspect, is offering a reward of up to $20,000 for information leading directly to Decker's arrest.

The Kittitas County Sheriff's Office and the Washington Army National Guard are also assisting in the ground and air search.

"At this time, we do not have any additional information that would suggest there is a threat to public safety, particularly within the back country and remote areas of our region," the Chelan County Sheriff's Office said in a press release on Tuesday. "However, we still encourage everyone who is outside recreating to remain vigilant and report any suspicious information to law enforcement."

Amid the manhunt, the Kittitas County Sheriff's Office asked the public to remain alert "for a suspicious person or circumstances," especially in the Teanaway valley and Blewett Pass areas.

Last week, the Chelan County Sheriff's Office said tracking teams believed they had spotted Decker in the Blewett Pass area. A hiking party had recently reported spotting a lone hiker in the Enchantments area who seemed ill-prepared for the trail and weather conditions and "appeared to be avoiding others," the sheriff's office said.

Decker, who is described as 5 feet, 8 inches tall with black hair and brown eyes, was last seen wearing a tan or green shirt and dark shorts, according to the sheriff's office.

Arianna Cozart, the attorney for Whitney Decker, the ex-wife of the suspected murderer and mother of the three girls killed, previously told ABC News that Decker struggled with mental health issues, including PTSD, and was unable to receive help through veterans' resources.

The father "had some mental health issues and some instability in his life" that led to restrictions regarding overnight visitation and taking his daughters out of the area, but before the girls disappeared, "there were no red flags," Cozart said.

The girls had each been found with plastic bags over their heads and their wrists were zip-tied, according to court documents previously obtained by ABC News.

An autopsy determined the girls' cause of death to be suffocation and the manner of death is homicide, the Chelan County Sheriff's Office said on June 9.