More than 170 pounds of methamphetamine was seized in Minneapolis by police and federal agents this week in what is believed to be the largest single meth bust in Minnesota history.

After months of surveillance, authorities entered a home in the 3600 block of Dupont Avenue N. on Tuesday to find nearly 40 packages containing about 4.5 pounds each of methamphetamine, as well as a sawed-off shotgun, 1.1 ounces of tar heroin and several thousand dollars in cash, according to a report released Friday by the Cannon River Drug and Violent Offender Task Force.

Fernando Ramos Meza, 33; Peter Martin, 34; Javier Lopez, 46; and Juan Daniel Valdez Mendoza, 23, were arrested at the residence and are being held with bail set at $1 million. Meza, Lopez and Mendoza were charged with first-degree possession of more than 50 grams of methamphetamine and first-degree sale of more than 17 grams. Martin was charged with felony possession of a short-barreled shotgun.

The Cannon River task force, made up of agents from the Rice and Le Sueur county sheriff’s offices and Faribault and Northfield police, began the investigation in January, following the drugs into Minneapolis.

The use of meth has been steadily climbing in Minnesota since 2009, said Carol Falkowski, one of the state’s foremost experts on drug abuse.

“And there are really no signs of it abating or leveling off any time soon,” said Falkowski, a former director of the alcohol and drug abuse division at the state Department of Human Services.

The first epidemic of the drug peaked in 2005, when its use quickly dropped for a few years after federal laws restricted the sale of over-the-counter drugs used to manufacture it.

The laws helped curtail small-time meth labs and local operations around the state, Falkowski said. But those labs were quickly replaced by cartels that produce the drug in Mexico and ship it throughout the United States, she said.

By 2012 and 2013, it was clear by the amount of methamphetamine that was being seized by police, the number of people admitted to addiction programs and the amount of overdose deaths that more people than ever were using the drug in Minnesota, Falkowski said. And those numbers have been increasing every year.

Officers did an “outstanding” job following the drugs to the Dupont Avenue N. home, said Rice County Sheriff Troy Dunn.

“Meth is still here,” Dunn said. “We combated and won the manufacturing of it when the over-the-counter laws were changed. But it is still coming up our interstate. We need to continue to battle this war against these dealers who are harming our residents and victimizing our communities.”

The task force worked with Minneapolis police and the U.S. Department of Homeland Security.

Police estimate that if sold wholesale, the methamphetamine would have brought about $4,000 per pound, or about $684,000 total. Supply has increased over the past 10 years, when the drug could have sold for about five times that. When the drug is sold to users at street level, it goes for as much as $100 a gram, which would make the seizure worth about $7.7 million, according to the task force.

“Methamphetamine is still big business in Minnesota,” Faribault Police Chief Andy Bohlen said in a statement. “Drug trafficking organizations bring meth to major metropolitan hubs like Chicago and Minneapolis, then break down the product for mid-level dealers.”