() The Washington sheriff’s department overseeing the manhunt for Travis Decker, the man accused of killing his three daughters, has indicated there is “no certain evidence” that Decker is alive or still in the area where authorities believed him to be hiding.

The Kittitas County Sheriff’s Office announced in a social media post late Monday that a search for Decker that involves several agencies continues despite early strong investigative leads regarding Decker’s whereabouts giving way to “less convincing proofs.”

The agency said that it has received scores of leads and tips about Decker’s location and that detectives and deputies have maintained extra patrols in several locations to try to locate the 32-year-old Washington man.

“Still, we can’t and won’t quit this search,” the department said in a news release announcing that Decker remains at large, adding that the three girls allegedly killed by their father deserve justice.

The search for Travis Decker

Decker has been missing since May 30, when authorities said that he took his three daughters during a parental visit and never returned the girls to their mother’s home. The girls, ages 5, 8 and 9, were found dead near a campsite on June 2, and an autopsy determined that the girls died from suffocation.

Since then, authorities said that thousands of hours have been devoted to trying to locate Decker, who police warned should be considered dangerous. The search has included federal agencies, including the U.S. Marshal’s Special Operations Group, along with the U.S. Border Patrol’s Tactical Unit as well as local sheriff’s deputies.

Photos released by the U.S. Marshal’s Office show agents from the federal agencies in mountainous terrain and also displayed photos of a sheriff’s department helicopter being used to search for Decker.

Those involved in the manhunt have spent days and nights in remote terrain and are working with K-9 units and experienced trackers to identify and follow “any credible lead” to what may be Decker’s location, the Kittitas County department said Monday.

The department is still asking the public to offer tips on possible sightings of Decker, who has a military background. The local law enforcement agency said it remains prepared to deploy resources and call partners in if new evidence points to where Decker may be.

However, the department said that some search resources are being allocated to find and recover Decker if he died in the rugged wilderness over the past three weeks.

Authorities called that possibility one that “increases every day.”

The department said that deputies and detectives “want nothing more” than to bring Decker to justice and believe public awareness is the best tool to make that happen.

Decker claims he never took his girls anywhere unsafe

Decker, who is homeless and would often sleep in his vehicle, in motels and at campgrounds, said in a recently released courtroom recording that he had previously lost his overnight custody rights to the girls before their deaths. Before that, though, he said he always took his daughters to safe, paid campsites.

“Every time I’ve had the girls, we have been in campsites and national forests and paid campsites that have campers. We’ve never done anything that was unsafe or anything I wouldn’t want to put myself in,” Decker said in the audio, which was from last fall.

Court documents cited by NBC News indicated that the girls were found zip-tied with plastic bags over their heads at the campground, which is located about 130 miles east of Seattle. The court documents indicated that Decker was previously ordered to seek mental health treatment and domestic violence anger management counseling but had refused.

Police have said that Decker remains a danger to the public as long as he’s at large. Relatives have told authorities that Decker can survive being outdoors for long periods of time. Authorities have also suggested that Decker’s physical appearance may have changed since the search began.

Chelan County Sheriff Michael Morrison told that anyone who showed sympathy toward Decker would be misguided. Morrison said that he hopes that Decker can still be found alive.

“That is our hope. That’s ultimately up to him, but we would like him to have his chance to sit in front of our judges and to face justice,” Morrison said. “And we want to make sure that (Decker’s daughters’) voices are heard. Their story is heard and that their killer is faced with justice.”