After more than six months of investigation, local and federal authorities have not come up with enough evidence to file criminal charges in connection to five fentanyl-related deaths in Commerce City in February.

On Feb. 20, five people were found dead inside an apartment. They had all died of unintentional fentanyl overdoses after ingesting cocaine, not realizing the drug had been laced with deadly fentanyl.

“Unfortunately, after six months of this intense undertaking, the evidence that exists today has not and will not lead us to an arrest or the filing of a charged case. We will continue to investigate any new leads that may come in,” Adams County District Attorney Brian Mason said Wednesday in a news release.

The Commerce City Police Department, the U.S. Drug Enforcement Agency, the U.S. Attorney’s Office for the District of Colorado, the North Metro Drug Task Force, and Mason’s office have “followed numerous leads, reviewed surveillance video, conducted countless interviews, obtained and evaluated cell phone data, utilized DNA, and exhausted every possible piece of evidence that might lead to the source of the fentanyl that caused these deaths,” the release said.

Fentanyl deaths in Colorado increased more than tenfold in the past five years — from 81 in 2017 to more than 900 in 2021 — and there is no indication they’re slowing. Fentanyl killed more Coloradans last year than homicides or traffic crashes.

Family members of fentanyl overdose victims in Colorado have been critical of police investigations, claiming that not enough is being done.

The people who died in the North Range Crossings Apartments, along 104th Avenue, are: Sabas Daniel Marquez, 24; Karina Joy Rodriguez, 28; Stephine Sonya Monroe, 29; and Humberto Arroyo-Ledezma, 32; and Jennifer Danielle Cunningham, 32.

A 29-year-old woman and a 4-month-old infant were inside the apartment and survived the incident.

“On February 20, 2022, our community became the latest example of the unrelenting toll fentanyl is taking on communities across the country,” Mason said. “That night five of our residents died from fentanyl poisoning in one of the largest mass incidents of this sort in the United States. My heart goes out to the families and friends of those who died in this tragic incident in February.”