A flash-bang grenade tossed into a stash house in Hartford, CT, Tuesday night kicked up powdered fentanyl and heroin that SWAT officers raiding the building breathed in, police said.

Eleven of the officers were taken to a hospital to be treated for their exposure to the deadly opioid.

Following weeks of investigating by Hartford and East Hartford detectives into a suspected heroin operation, they learned that heroin was being bagged at the apartment for street-level sale, Deputy Chief Brian Foley said.

With information that a large amount of heroin and firearms were in the home, the Hartford department's emergency response team joined detectives to raid the home about 7:30 p.m., Foley said. Making what Foley described as a tactical entry, the flash-bangs, meant to stun anyone in the apartment, went off and turned powdered drugs on a table into an aerosol, the Hartford Courant reports.