Almost three quarts of fentanyl and other illegal drugs and guns were seized at a raid at a home in Bloomington last week, the Hennepin County Sheriff's Office said Tuesday.

Thursday's raid was the largest amount of the dangerous opioid ever confiscated in Minnesota. The 2,754 milliliters had an estimated street value of $275,000, authorities said.

Fentanyl is a narcotic that typically had been used in hospitals for strong pain relief. As a street drug, it is 50 times stronger than heroin and has been tied to dozens of overdoses and deaths. It is sometimes added to heroin and sometimes sold straight to unwitting addicts. The rock star Prince died of a fentanyl overdose at his Paisley Park mansion.

There were 18 fentanyl overdose deaths in Hennepin County from January to September this year, the Sheriff's Office said. In 2015, there were nine; in 2014, five. Heroin overdoses have caused 49 deaths in the county in the first nine months of 2016 compared with 48 in all of 2015.

The drug comes in the form of a pill, a patch or a liquid that can be injected. Experts say that the difference between a therapeutic dose and a deadly dose is very small. As with an opiate, the main symptoms of fentanyl abuse are euphoria, drowsiness, lethargy and mellowness. Fentanyl very quickly creates a tolerance to high doses, so a dose that is adequate for the intended high one week will probably not create that intended high even a few days later.

"Unfortunately, there is too much of this poison out there and people are dying — too many people are dying," said Sheriff Rich Stanek. "We directed narcs to turn over every stone and find what's out there and where it's coming from — look what they found. [This is] just the beginning, not the end of it.

"This is what we accomplish with multiagency partnerships," Stanek said. "Working together, our agencies can achieve success in preventing overdose deaths from opioids like fentanyl and heroin. If you want to deal this poison in Hennepin County, we have a place for you in the jail."

Authorities said marijuana, illegal prescription drugs and several guns also were seized in Thursday's raid.

The raid was conducted by the Bloomington SWAT team on behalf of the Hennepin County Violent Offender Task Force. In October, Hennepin, along with Anoka, Dakota, Ramsey and Washington counties, were designed as "high-intensity drug trafficking areas" by the White House Office of National Drug Control Policy. The designation will provide the five counties with federal resources to help with the coordination and development of drug control efforts.

The Hennepin County Violent Offender Task Force includes the Sheriff's Office, as well as the Brooklyn Park, Brooklyn Center, Golden Valley and Richfield police departments.

Pat Pheifer • 612-673-7252