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Authorities say they're still looking into the sources of heroin that caused two deaths and several other overdoses last weekend across the metro.

Two clusters of overdoses were particularly unsettling, authorities said — five cases were reported within 30 minutes of one another in the south metro Friday evening and six cases surfaced Saturday in Anoka County, where the deaths occurred.

The Anoka County Sheriff's Office said the heroin in their cases likely came from one source, but it's unknown whether the drug was cut with another narcotic or why it was so deadly.

"We have no idea where [the drugs] came from," said Anoka County sheriff's Cmdr. Paul Sommer. "I don't know if it's tainted. I don't know if it's super potent. We just don't know."

Sommer said there was no heroin left at the six different scenes to test, but that the timing and geographic proximity of the cases led authorities to believe the drugs had the same origin. Police are unaware of any relationship among the people who overdosed in Anoka County; they were not together at the time.

"It's alarming and it's an aberration and it's outside the norm," Sommer said.

The overdoses occurred between 5:31 a.m. and 2:48 p.m. involving five men and one woman ranging in age from 20 to 30.

The Sheriff's Office and the Midwest Medical Examiner's Office declined to identify the 22-year-old Fridley man found dead in Fridley and the 23-year-old Ramsey man found dead in Anoka.

The Sheriff's Office refused to release addresses where the overdoses occurred or the names of the victims or other witnesses, citing an ongoing criminal investigation. The medical examiner's office said that its findings were pending.

Friends on social media identified one of the men as John Koscielski. His family could not be reached for comment.

Anoka County deaths

In Fridley, police responded to a predawn call about a 22-year-old man who had overdosed on heroin and was pronounced dead at the scene. Evidence collected there as well as statements from family members led officers to believe the illicit drug had contributed to the man's death, according to authorities.

Later that day, Fridley police were dispatched to Unity Hospital where they found another overdose victim in his vehicle, said Lt. Ryan George.

The rash of overdoses began in the south metro with three calls to the Mall of America, one call to western Bloomington and one call to the Prior Lake area coming in within a half-hour of one another Friday.

Jeffrey Lanenberg, south metro ambulance manager for Allina Health EMS, said the number of calls wasn't unusual for a weekend, but that the timing was unexpected.

"This was odd because it was all coming in at the same time," Lanenberg said. "The most common question coming in this weekend was, 'Was some kind of bad batch coming in?' I wouldn't know that. It just happened."

Each call was "life-threatening," he said, but the patients recovered. Lanenberg declined to speak in more detail about the specific cases, citing federal health privacy protections, but said an emergency drug, Narcan, is regularly deployed via nasal spray, injection or intravenously to reverse the effects of an overdose.

Cases at Mall of America

Bloomington authorities said it's unclear exactly what type of drug or mixture of drugs was to blame in the Mall of America cases.

"The information we got at the scene was that the two people … had used a combination of narcotics that evening, including one we believe is an opiate," said Bloomington Police Deputy Chief Mike Hartley.

A 35-year-old woman and 34-year-old man, both from Minneapolis, were treated at the mall's south food court about 8:18 p.m. Friday. The man was unconscious and the woman began losing consciousness when police arrived. Both regained consciousness and were taken to a hospital for treatment.

A man was stopped outside the mall about 8:37 p.m. and was treated for an overdose. He had been with the other two at some point, Hartley said.

Hartley said the Bloomington cases are being treated as medical calls and not criminal investigations. The two deaths in Anoka County are being investigated as criminal matters, Sommer said, while the other overdoses are considered "a component" of those investigations.

Authorities said that they have no information linking the two clusters of overdoses, but they haven't ruled out a possible connection.

"We have no way to know for sure," Sommer said.

Minneapolis had seven overdose calls this past weekend, six of them "priority one" calls, which mean someone's life is at risk, said the department's spokeswoman, Sgt. Catherine Michal. It's unclear whether those were heroin-related, she said.

According to Police Clips, St. Paul police were called to the CVS on Snelling Avenue about 12:15 a.m. Friday for a woman who had allegedly overdosed on heroin and found her unconscious and barely breathing.

Staff writer Hannah Covington contributed to this report.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib