Two men have been arrested after officials said an investigation found they were dealing “significant” amounts of fentanyl and other narcotics in Boulder County and the Denver-metro area.

Carlos Centeno-Izaguirre, 43, and Gerson Arteaga-Izaguirre, 20, are facing numerous charges including multiple counts of unlawful distribution of fentanyl — more than 50 grams, conspiracy to distribute a controlled substance, and special offender — distribution within 1,000 feet of a school, all Class 1 drug felonies.

Centeno-Izaguirre is also facing one count of distribution of fentanyl resulting in death for reportedly selling the drugs that resulted in an overdose death.More information on the death was not released by officials.

According to a release, the Boulder County Drug Task Force spearheaded the investigation and seized more than 500 grams of fentanyl, along with smaller amounts of cocaine, morphine and heroin.

The Federal Bureau of Investigation, the Boulder Police Department Special Enforcement Unit and the Longmont Department of Public Safety’s Special Investigations Unit also participated in the investigation.

“I appreciate all the hard work that the Drug Task Force, other law enforcement partners, and our prosecution team have dedicated to this tragic case,” Boulder County District Attorney Michael Dougherty said in a statement. “Fentanyl dealers should be held fully accountable for the destruction they inflict, and we are committed to pursuing justice in this case.”

According to an affidavit, members of the Boulder County Drug Task Force were told by a confidential informant in September that Centeno-Izaguirre was coming up from Aurora to conduct large drug deals in Boulder involving “M30” pills, counterfeit oxycodone pills containing fentanyl.

Under the supervision of the task force, the confidential informant made several buys with Centeno-Izaguirre for 500 to 1,000 pills in September and October, with some of those deals occurring in parking lots within 1,000 feet of different schools.

According to the affidavit, Arteaga-Izaguirre was also at some of the buys driving Centeno-Izaguirre.

Centeno-Izaguirre is being held on $500,000 bond while Arteaga-Izaguirre is being held on $350,000 bond. Both men are set for preliminary hearings on Thursday.