Human remains, believed to be of a man wanted on suspicion of murdering his three daughters, aged nine, eight, and five, have been found in the US state of Washington.

Police had been searching for Travis Decker since officers discovered his phone and the bodies of his daughters—Paityn, Evelyn, and Olivia—in a remote campground on June 2. His truck was also located in the vicinity.

While positive identification has not yet been confirmed, preliminary findings suggest the remains belong to Travis Decker, according to the Chelan County Sheriff's Office.

The remains were discovered in a remote wooded area south of Leavenworth, Washington.

Decker, 32, faced charges of kidnapping and first-degree murder, with authorities believing he had been hiding in a remote part of the mountainous state.

The girls' mother reported them missing on May 30, after Decker did not return them to her home in Wenatchee following a visit and did not respond to her calls.

The children had died from apparent suffocation, and their wrists were reportedly bound with zip ties, according to officials.

Decker was previously a soldier and was thought to possess skills that could help him evade capture in a mountainous environment.

The remains were found on Grindstone Mountain, just a few miles from where the girls' bodies were discovered.

A reward of $20,000 had been offered for information leading to Decker’s apprehension, prompting widespread closures of national parks popular for hiking in the area.