By Peter Holley

Georgia authorities said up to four people have died and dozens more have become ill in south and central Georgia after overdosing on an unknown street drug. (Photo: Bibb County Sheriff’s Office/WSB)

The small yellow pills look like prescription drugs from a pharmacy, but Georgia authorities say they're anything but.

In recent days, the drugs — which are purchased on the street — have led to dozens of overdoses and as many as four deaths in south and central Georgia, state health officials told the Atlanta Journal-Constitution.

As the number of overdoses increases, authorities say they're scrambling to keep pace. The state is already battling a growing opioid crisis, authorities say. On Wednesday, the Georgia Bureau of Investigation reported six additional overdose cases potentially related to the drug.

“We try to warn the public, but people are still buying these counterfeit pills off the street thinking they're legitimate preparations, but they are not,” Georgia Bureau of Investigation spokeswoman Nelly Miles told The Washington Post. “It may be marked as something legitimate, but — chances are — it's not.”

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In a Georgia Department of Public Health statement released Tuesday, authorities said patients reportedly thought they were purchasing Percocet, an opioid pain medication.

The yellow pills actually contained another “extremely potent” substance that investigators are rushing to identify, the statement noted.

“First responders say patients are unconscious or unresponsive and have difficulty breathing or have stopped breathing,” the statement said. “Many patients need to be placed on ventilators.”

To counteract the substance's effects, patients required “massive doses of naloxone (Narcan)," the statement added.

The key now, the Georgia Bureau of Investigation's Miles said, is identifying what exactly is inside the mysterious yellow pills.

“We are assisting with testing with the evidence that could potentially be related to the outbreak,” she said. “Law enforcement is working around the clock. “They received some pills today and completing the testing is a priority.”

According to the Bibb County Sheriff's Office, the counterfeit pills “have the numbers 10/325 on one side and the word PERCOCET in all capital letters on the opposite side.” The agency noted that the word PERCOCET is “not stamped as deep as the manufacturer typically does on their pills” and is “at an angle.”

Doctors typically give opioids to patients seeking relief from severe pain following surgery or after an accident, according to the Georgia Prevention Project. By triggering the release of neurotransmitters like dopamine, the drugs stimulate the brain's reward system while simultaneously blocking the signals that alert the brain to feelings of pain.

The result, according to the nonprofit group, is a “pleasurable and often euphoric feeling.”

Though the drugs relieve pain, they can also lead to “physical dependence, respiratory depression, euphoria, reduced intestinal motility and other desired and undesired effects,” the group reported in a study about the state's opioid epidemic released last year.

Chuck Rosenberg, acting administrator of the Drug Enforcement Administration, told NBC News that despite being home to 5 percent of the world's population, the United States consumed “an overwhelming percentage of the world's prescription pain medication” — especially “hydrocodone and oxycodone.”

Opioids killed more than 33,000 people in the United States in 2015, according to the Centers for Disease Control and Prevention. At the time, the CDC reported, that number was higher than any other year on record.

In 2016, however, the number may have topped 59,000, according to a New York Times report that relied on preliminary data to estimate the spike in deaths.

“The individuals that are involved in the drug trade, this may be their newest product,” Sheriff David Davis of Bibb County told CNN. “We need to know who's putting this poison in the community right now.”