Authorities continue to investigate a wave of overdoses linked to a superstrong batch of heroin circulating in Butler County.

The investigation is a priority and some progress has been made, according to Butler County District Attorney Richard Goldinger.

“We have some leads about who may be the source of this,” Goldinger said this morning. He did not cite specific information.

The “extremely strong batch of heroin,” said county Detective Tim Fennell, who leads the Butler County Drug Task Force, is believed responsible for at least two deaths and as many as a dozen near fatal overdoses in the past week alone.

Fennell and Goldinger on Friday took the unusual step of issuing a public warning about the potentially lethal heroin.

The advisory was prompted after authorities learned of at least five near fatal overdoses handled Friday during one shift at the Butler Ambulance Service.

Crews repeatedly had to use the drug naloxone, also known by its trade name Narcan, to reverse heroin overdoses.

In most of the cases, Fennell said, paramedics administered double and triple the doses of Narcan to bring the users out of their life-threatening stupors.

County drug officials do not know if the heroin has been laced with the powerful painkiller fentanyl, unknown chemicals or other substances.

“We’re still waiting for toxicology results,” Fennell said. The evidence is being analyzed by the state police crime lab in Greensburg, Westmoreland County.

Investigators suspect the toxic batch of heroin comes in light blue stamp bags with no markings or names on them.

Fennell said he believes the potentially deadly heroin is “localized” and apparently has not hit other counties, such as the lethal batch of so-called “Theraflu” did last year.

In 2014, at least 22 people in Western Pennsylvania, including three in Butler County, died from a single batch of fentanyl-tainted heroin stamped with the name Theraflu.

Fennell said investigators have spoken to some of those who overdosed last week in hopes of tracking down the source of the drug.

If identified, the seller of the heroin could face a top charge of drug delivery resulting in death, a first-degree felony that can result in a multiple-year sentence for dealers.

Bringing criminal charges, Goldinger noted, is one of the overall goals of curbing heroin deaths.

While local law enforcement and health officials issued the warning to people about the dangerous heroin being sold, Goldinger acknowledged the message could backfire.

“Addicts hear about this and some will now seek it out,” he said. “A dangerous drug can become more desirable to addicts.

“But with what we’re seeing here, we have to get the word out because people are going to die.”