DENVER — Two men arrested during a Denver police raid are facing federal charges after police say they found a “brick” of fentanyl that led to a public health bulletin earlier this month, according to a release from the U.S. Department of Justice.

Gilbert Franco Garcia, age 38, and Jesus Aviles-Higuera, age 29, appeared before a U.S. magistrate judge Friday, where they were advised of the charges of possessing fentanyl with the intent to distribute it.

The suspects were arrested November 1 when members of the Denver Police Department executed a search warrant at 4860 West Mexico Avenue.

During the raid, police said they found 1 kilogram of fentanyl, most of which was in the form of a dark-colored brick; approximately 134 fentanyl pills; about 454 grams of black tar heroin; and nearly 75 grams of cocaine, the release read.

Officers initially suspected the dark-colored brick was black tar heroin, and the pills were Oxycodone. However, laboratory testing revealed the only controlled substance in the brick, and the pills were fentanyl, according to justice officials.

The Mexico Avenue operation prompted Denver health officials and police to issue a public health bulletin, warning of the increased overdose danger.

The synthetic opioid can be up to 50 times more potent than heroin and 100 times more potent than morphine. Overdoses on fentanyl typically occur faster than other drugs. It is so strong that just touching or breathing in can be harmful.

Garcia and Aviles-Higuera are scheduled to appear in court this week for a detention hearing.