ANOKA COUNTY, Minn. - The Anoka County Sheriff's Office calls it an "alarming anomaly."

Six people overdosed on heroin on Saturday. Two of them died, three others survived and one other is in critical condition. At least four were men in their mid-20's, and one was a woman, according to the agency.

Commander Paul Sommer said in a written statement: "This is an alarming number of overdose cases to happen so close together in time frame and geography. Although it is only speculation at this point, we are concerned about the possibility of a quantity of heroin that may be the single source of these overdose cases."

Sommer says the users were from Andover, Anoka, Fridley, Ham Lake, and Isanti. The latter person was taken to a hospital in Coon Rapids, which is in Anoka County.

The cases were first reported at around 5:30 a.m. with the latest case in Ham Lake reported to KARE 11 Saturday evening.

Sommer calls the investigation "extremely difficult" in trying to get those involved to cooperate with authorities.

Anoka County has not been immune to the heroin crisis. In 2014, it held a series of public forums to educate families about the issue.

Adam Pederson, of Minnesota Adult & Teen Challenge, a drug and alcohol recovery and treatment program, was part of those forums. He also works with kids in the Anoka school system educating them of the risks of drug use.

"The ones that we've interacted with in Anoka County are not your typical heroin addicts. They can be your neighbor, they can be the person down the street," said Pederson.

He said in 2013, there were at least 29 heroin overdoses and at least 10 deaths. He says, the numbers have gone down the past two years, but it's still a problem.

"Duluth for some reason and Anoka County have been identified as high traffic areas in the state of Minnesota. We have a lot of it unfortunately," said Pederson.

Last school year, a survey was done at Anoka County high schools. It was part of the "Know the Truth" program through MN Adult & Teen Challenge. More than 3,000 students were surveyed and among them, 32 percent of students had reported having used illegal drugs. Of those that used, 38 percent had reported using prescription pills and 3 percent of users had reported using heroin.