Bones were found near a Cascade Mountains campground amid the manhunt for the 33-year-old suspected of killing his three young daughters, the FBI said on Friday.

The bones are being analyzed to determine if they’re human, FBI Seattle spokesperson Ted Halla said.

“We can confirm that some bones were collected as part of the search activity earlier in the week around the Rock Island Campground,” he said by email.

The Cascade Mountains campground near Leavenworth, Washington, is the location of the discovery of the bodies of Travis Decker’s three daughters, Paityn, 9; Evelyn, 8; and Olivia, 5, on June 2.

Decker’s pickup was also found nearby, on land described by the Chelan County Sheriff’s Office as “rugged and heavily forested terrain,” about 150 miles east of Seattle.

Earlier this month, the office said DNA from plastic bags found on the girls heads matched that of the father, and no other human DNA besides the girls’ own was found. The county medical examiner concluded the girls died by suffocation and are the victims of homicide, the sheriff’s office said.

Following the discovery of their bodies, local, state and federal authorities launched an extensive manhunt for Decker, fearing he could use his military background and outdoors experience to vanish.

Decker was charged with three counts of first-degree murder and first-degree kidnapping and is the subject of an arrest warrant.

On May 30, his ex-wife reported Decker did not return the girls after a planned visit, authorities said. The report wasn’t enough to trigger an Amber Alert, Washington State Patrol said, noting that a late return is not necessarily an abduction and that there was no imminent threat of violence.

Investigators said motive was unclear. Court filings state Decker refused to sign a parenting plan nearly a year ago that included orders to seek mental health treatment and anger management counseling.

On Monday, Chelan County Sheriff Michael L. Morrison outlined the two-day search for evidence near the campground on federal land that started Monday and drew roughly 100 police, deputies and federal agents.

“Over the past three months, investigative teams, led by your Sheriff’s Office Investigative Unit, have pursued every lead and searched vast, remote areas in the hope of locating Travis Decker or any evidence that might bring us closer to answers,” Morrison said in a statement.

The sheriff repeated that it’s not clear if Decker is alive.

“At this time, no conclusive evidence has been found to indicate whether Travis Decker is alive or deceased,” he said. “We continue to follow every credible lead.”