Three women and a man from Sanford have been arrested on heroin trafficking charges.

Ashlyn Smith, 26, was arrested Thursday on two counts of aggravated drug trafficking. The other suspects were arrested earlier this month.

“For the past two months, agents assigned to the Maine Drug Enforcement Agency’s York District Task Force have been investigating the sale of heroin in Sanford by the four,” said Stephen McCausland, spokesman for the Maine Department of Public Safety, in a press release.

McCausland said investigators have not determined whether the suspects had any connection to the six drug overdoses that occurred in Sanford in a 24-hour period last weekend. One of those people who overdosed, a 44-year-old man, died.

Sanford Police Chief Thomas Connolly suspects that the drug involved in the overdoses was fentanyl, an opioid painkiller that is as much as 50 times as potent as heroin. The substances found at some of the overdose scenes are still being tested by the state Medical Examiner’s Office.

Also charged with aggravated drug trafficking were Ian Blow, 25, Samantha Barnett, 25, and Stephanie Meunier, 26.

McCausland said members of the task force and Maine State Police stopped a car in Lebanon on June 2. Blow, Barnett and Meunier were in the car, returning from Lawrence, Massachusetts, with heroin that police believe was going to be sold in the Sanford area.

Police also seized 25 grams of a heroin/fentanyl mix during the traffic stop.

Blow, Barnett and Meunier are being held in the York County Jail on $25,000 cash bail.

Smith, who allegedly sold heroin to undercover drug agents, was arrested at her home Thursday and taken to the county jail, where she is being held on $50,000 cash bail on each trafficking count.