Authorities are analyzing several items found in the Washington wilderness to see if they are connected to Travis Decker, who stands accused of killing his three daughters before fleeing.

The FBI cordoned off extensive areas around the Rock Island Campground on Monday and Tuesday in a thorough search effort for the fugitive father.

Approximately 100 team members scoured over one million square acres, equivalent to 247 acres, of challenging terrain under the scorching summer sun, in hopes of uncovering any hints of his location.

Decker went on the run in early June after allegedly suffocating his daughters, Paityn, 9, Evelyn, 8, and Olivia, 5, before a custody exchange with his ex-wife in Leavenworth, Washington.

The girls were found in his abandoned truck on June 2 at the Rock Island Campground after he failed to bring them to their mother on May 30. Decker was nowhere to be found. 

FBI Seattle Special Agent in Charge W. Mike Herrington said ‘several items’ were recovered which could be of significance.

‘Finding this potential evidence emphasizes the value in having various teams search an area multiple times, especially in such challenging conditions,’ he said. 

The mission was to locate Decker or discover signs that he had been in the area, or otherwise new evidence about the crimes he is accused of committing. 

Search crews, comprised of officers from two sheriff’s offices, the U.S. Marshals Service, two police departments and Central Washington University’s anthropology department, used electronic mapping to document the scope of their search.

They ultimately went beyond their planned perimeter to cover as much ground as they possibly could.

The FBI said while they led this particular search operation, the Chelan County Sheriff’s Office is still the lead on the overall investigation. 

Chelan County Sheriff Mike Morrison insisted investigators ‘have not given up’ on finding him.

‘We understand the frustration, we feel it as well,’ he said at a news conference Monday night.

‘We will not relent, we will not give up until Travis Decker is taken into custody.’

‘This is not going to go away until Travis is located’ whether he is alive or not, the sheriff continued, as he expressed doubts about the former soldier’s ability to survive in the wilderness this long despite his military survival training.

‘He has to be perfect every single day,’ Morrison explained. ‘We just have to be perfect once.’ 

Police said he was also homeless and living out of his car by the time he picked up his three girls from their mother’s house on May 30.

His ex-wife Whitney told police she didn’t believe Decker was dangerous, and that he loved his daughters, with whom he had a ‘good relationship.’ 

A $20,000 reward is on offer for any information leading to Decker’s arrest.

Authorities have warned Decker could be armed and dangerous, and citizens are warned not to approach him.

He is wanted on three counts of first-degree murder and one count of first-degree kidnapping.