Chris and Shanann Watts.Photo: Shanann Watts /Facebook

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When the bodies ofShanann Watts and her two young daughterswere discovered at a remote Colorado oil fieldin mid August, police found something else at the scene which may further link the three deaths toChris Watts, Shanann’s husband and the father of her girls.

In the filing, dated Tuesday, authorities requested to take a print of Chris’ bare feet so they can determine if it matches those found on the bag.

A source close to the investigation confirms to PEOPLE that a bag bearing a possible footprint was found at the oil site, some 40 miles east of the Watts home.

But the source declined to divulge the size or the material of the bag.

Chris Watts.Joshua Polson/AP/REX/Shutterstock

Christopher Watts court case, Greeley, Colorado, USA - 16 Aug 2018

“There was a lot of evidence collected at the scene,” the source says. “and each piece is being carefully inspected to see if it pertains to the case or not.”

Citing “numerous items of evidence” that are being tested, prosecutorshave sought to obtainChris’ DNA and fingerprints as they continue to build a case against him.

The defense has vigorously disputed this request, describing it as too vague and lacking established probable cause. The judge has not yet ruled.

Chris has been sitting in the Weld County Jail for more than a month.

He was arrested late on Aug. 15 andcharged with first-degree murder, among other crimes,in the deaths of 34-year-old Shanann, who was 15 weeks pregnant, and daughters Bella, 4, and Celeste, 3.

The three were reported missing on Aug. 13, not long after Shanann returned from a work trip, and authorities announced their bodieswere found on the property of Chris’ former employer Anadarko Petroleumwithin hours of him being taken into custody.

Anadarko fired Chris the same day as his arrest.

Shan’ann Watts (center) and her daughters.Shanann Watts /Facebook

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Afterward, he confessed to “the truth,” the affidavit states — claiming he strangled Shanann in a rage after watching her strangle Celeste when he told her he wanted to separate. Bella was seen apparently lifeless on her bed, according to the affidavit.

He allegedly told police he then hid all three bodies at the oil site.

However, a source close to the investigation previously told PEOPLE that “there is absolutely no evidence that she [Shanann] killed her children.”

“Just based on the preliminary evidence, everything is consistent with him killing them all,” the source said.

Chris has not yet entered a plea. His lawyer did not respond to PEOPLE’s requests for comment but,according to a statementfrom the state’s public defender’s office, their attorneys are barred from discussing ongoing criminal cases.

source: people.com