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GOLDEN, Colo. — The FOX31 Problem Solvers have learned the death of inmate Zachary Green at at the Jefferson County detention facility Saturday morning is being investigated as a possible fentanyl overdose.

In a press release, the Jefferson County Sheriff’s Office said Green’s “death does not appear to be suspicious” but did not clarify to say it was likely due to a drug overdose.

One inmate, who like Green was in the jail’s work release program, told FOX31 he finds a death by fentanyl to be very suspicious since inmates shouldn’t have access to drugs behind bars.

“I don’t know what they would consider suspicious but I do feel they should be kind of held responsible,” said the inmate, whose identity FOX31 has agreed to protect.

The inmate told the Problem Solvers that deputies didn’t do any up-close welfare checks through the night to make sure Green was breathing properly.

A spokeswoman says department policy is to do walk-throughs of inmate pods every 30 minutes. Green checked into the detention facility at 1 a.m. Saturday, Jan. 25 and was found unconscious at 8:45 a.m.

A department spokeswoman said deputies conducted 22 walk-throughs between 6 p.m. and 8:45 am, with two head counts during that time, but didn’t clarify if the head counts were done at 6 p.m. and 8:45 a.m. or when.

The inmate who spoke to FOX31 on condition of anonymity said after inmates notified deputies Green wasn’t breathing, deputies immediately moved all of the inmates out of the 3-C pod and conducted a search for drugs.

“As you know, we had somebody pass from fentanyl and we’re looking for fentanyl, so your stuff was rummaged through,” is what the inmate said one deputy told him, before the deputy added, “We did find doses of fentanyl that could’ve been deadly to everybody in here.”

The  inmate who spoke with FOX31 says he’s confident Green was given fentanyl by a fellow inmate.

“Definitely through inside the jail. It’s all around in there. It’s flooded in that system,” the inmate said.

He added work release inmates aren’t strip-searched when they return to the jail each night. However, the sheriff’s office says it does do strip searches on a random basis.

The inmate also said that while inmates undergo drug testing, fentanyl is not a drug that is typically screened.

“We are drug tested but, of course, people are going to look for the drugs that are not going to be found in your system. Fentanyl happens to be one of them,” he said.

Mike Taplin, a spokesman for the Jefferson County Sheriff’s Office, told FOX31, “We are declining to release the full range of substances for which the Sheriff’s Office routinely tests because such disclosure has the potential to compromise the testing program and could adversely impact the safety and security of the jail and our inmate community.”

But Sarah Urfer, a toxicologist who formerly owned the lab ChemaTox that did much of the drug screening for law enforcement agencies in Colorado, told the Problem Solvers fentanyl is not screened for in most standardized drug tests.

“Fentanyl is very scary as a drug. It’s highly potent, which means in really tiny quantities it can do a lot of damage,” said Urfer, who described fentanyl as 50 to 100 times more potent than morphine.

Urfer said it’s well known that drugs — and fentanyl in particular — are increasingly accessible in local jails.

“It’s very much lethal and people who are likely to take this drug, particularly in jail, are probably people who have addiction issues, which means their ability to dose and engage in safe behavior is going to be pretty low,” Urfer said.

The inmate who spoke to FOX31 about Green’s death believes deputies should’ve found him sooner when breakfast was served around 5 a.m. or certainly during the shift change between 6 a.m. and 7 a.m.

“I feel like it could’ve been prevented. If they did a simple welfare check on people, they probably could’ve saved his life,” the inmate said.

The sheriff’s office declined a request for an on-camera interview but a spokeswoman says Green’s death and whether a substance was involved is part of an ongoing investigation.

Green, 31, had been in the jail’s work release program since October after being sentenced in September for convictions related to domestic violence.