Authorities say police responded to six suspected opioid overdoses over a 24-hour period last weekend in Sanford, Maine.
The incidents included one death and happened between Friday and Saturday.
Police Chief Thomas Connolly told the Portland Press Herald on Tuesday that he believes the common substance among the overdoses is a small batch of fentanyl being sold as heroin. Tests haven't been returned to confirm his suspicion.
Connolly says a 44-year-old man was found dead in his apartment at around 5:40 a.m. Saturday. His identity hasn't been released.
The state Medical Examiner's Office is doing toxicology tests to determine what substance or substances killed him.
Connolly says investigators suspect that all of the overdoses can be linked to one dealer.
The Maine Drug Enforcement Agency is involved in the case.