SCHENECTADY — Four people overdosed in Schenectady during a two-hour span Thursday night sending police, firefighters and paramedics hopscotching around the city in a desperate bid to keep them alive.

All four survived.

One of the victims, a 29-year-old woman, told police she was supposed to start a treatment program Friday, just hours after what police said appears to be a dose of fetanyl-laced heroin nearly killed her.

The outbreak comes as the U.S. deals with a nationwide opioid epidemic. But Schenectady police commanders said the quick successions of overdoses was almost unprecedented.

"We unfortunately respond to overdoses on a regular basis but to have them all back to back in a short amount of time led us to believe that there is something more dangerous," said Lt. Thomas Kelly, who responded to the last two of those calls.

It prompted police to issue a dire warning Thursday night on Facebook alerting people that they were seeing a surge in overdoses that could imperil lives.

The woman, whose name police are not releasing, was one of four city residents, ranging in age from 29 to 60 years old, who police said were hospitalized after overdosing on heroin between 6 and 8 p.m. Thursday.

"It would appear that there is a different drug or some different compound," said Kelly, who responded to the last two of those calls.

Around 6:50 p.m., a neighbor called police to report that a 50-year-old man at Albany and Backus streets in the Hamilton Hill section was unresponsive and needed help.

Forty minutes later, Kelly was at Southgate Drive and Frank Street in the Central State Street neighborhood for a report called in by a friend of the 29-year-old woman.

In those cases, he said, those two people, even though they use drugs, were "caught off guard" by the mystery opioids. When he arrived they were unconscious, an indication the person took a drug they are not familiar with or too much of it.

"The two that I had talked to when they did regain consciousness, it was a powdered fentanyl that they said they had snorted," said Kelly, adding paramedics did not need to administer Narcan, a medication used to block the effects of opioids, especially in overdose.

The other two cases involved are a 30-year-old man in the area of State Street and the Gateway Bridge and 60-year-old man on Duane Avenue. Both were found unresponsive but later regained consciousness. The older man denied he was using heroin, Kelly said.

It was unclear if paramedics used Narcan.

The department's Special Investigations Unit and crime analysts are looking into the matter, said Kelly.

He and others involved with programs aimed at combating drug addiction stressed that heroin overdoses affect people from all walks of life.

Confronted with the disturbing trend, Kelly contacted Lt. Ryan Macherone, who has led the department's efforts through a fledgling program called Schenectady Cares to get addicts the help they need.

Macherone suggested they alert the public through a post that he wrote Thursday on the department's Facebook page.

"Luckily, because of the quick actions of dispatchers and the professional medical response they received from (the Schenectady Fire Department) and Mohawk Ambulance, all of these individuals should be OK," Macherone wrote.

"We write this tonight not as a scare tactic, but as a warning. Our officers will work to locate the source or sources, but we cannot stop what is already out in our community and the surrounding communities."

On Friday, Macherone said the post served as warning "that something pretty bad might be out there that's sickening people."

As of early Friday afternoon, the submission had been shared over 300 times.

Chad Putman with New Choices Recovery said Friday it's not uncommon for people struggling with heroin addiction to travel to an area where there have been or are a rash of overdoses or death in search of the "good stuff."

He said that his agency and their partner organizations work to make sure people with drug habits have clean needles, Narcan, don't use alone.

"If they have partner there, their partner sees that their lips are turning blue, their respiratory is reduced, and it looks like they're in bad shape, then the individual can run through a series of checkpoints and then say 'if you don't snap out of this, I'm going to give you Narcan,'" said Putman.

He said sometimes the mere mention of Narcan is enough to scare a person into halting their drug use.

They also distribute testing strips people can use to see if their heroin is laced with fetanyl, added Putman, director of New Choice's COTI (Center of Treatment Innovation), a project that focuses on providing treatment to people in communities affected by opioid addiction.

New Choices is involved with Schenectady Cares program where addicts are allowed to walk into the Schenectady police station and get help for their addiction through a network of agencies.

"What's beautiful about the police department is their doors don't close," he said, noting that as of Friday the organization had received five referrals though the program that they got into treatment programs. "Even if somebody isn't ready to stop using, it doesn't mean that there isn't other types of assistance that can be provided to keep them safe."

Schenectady Assistant Fire Chief Don Mareno said late Friday that so far this year firefighter paramedics have handled about 80 overdoses, which works out to about two every week.