"Testing done today in NY by the federal Drug Enforcement Agency confirms that samples of the substance that caused today's overdose cases on the New Haven Green are K-2, a potent, synthetic drug that induces marijuana-like effects", said Director of Communications for New Haven, Laurence Grotheer.
Emergency crews showed up and found some people passed out and unresponsive, while others were complaining of nausea or were vomiting.
Officials said the patients were "all different ages".
Another 5 people refused medical attention and were not in enough distress to be transported for treatment, he said.
"We have far fewer sleeping on the Green but the drug use is awful", he said.More news: Pakistan Navy celebrates Independence Day with traditional zeal
The Office of Emergency Management in New Haven said it is still fielding calls and the number of victims could increase. She also asked that the city be given larger supplies of the opioid antidote Narcan from the state Department of Public Health, said city spokesman Laurence Grotheer.
K2 is a synthetic cannabinoid related to marijuana that is frequently laced with other drugs, said Dr.
WVIT reports that the man arrested "is believed connected to at least some of the overdoses" and "had drugs on him at the time of his arrest, [but] has yet to be charged in any of the overdose cases".
No deaths were reported, but officials said two people suffered life-threatening symptoms. "It is taking people out very quickly, people having respiratory failure".
"Even while we were trying to return people to service, they were passing victims on the ground", Alston told reporters.More news: Subtropical Storm Ernesto forms in the Open Atlantic
"We heard from people on the Green that it potentially contained PCP, and some of the reactions in the emergency room suggest there was an opioid involved as well", said EMS Medical Director Sandy Bogucki.
According to police, one patient was non-responsive to Naloxone, which is a drug used to treat narcotic overdoses. The additives boost the high, but can create a unsafe, sometimes deadly cocktail.
More than a dozen people overdosed on synthetic marijuana at the same park on July 4. First responders sprinted across the park from victim to victim as more calls came in.
The CDC said a record 72,000 Americans died past year because of drug overdose - about 10 percent higher than previous figures. I'm also grateful to the state Department of Public Health for its quick response to our request for additional doses of Narcan, the antidote administered to several of those afflicted. They are still awaiting toxicology tests to confirm the exact substance.More news: Ex-Real Madrid boss Zinedine Zidane could be Manchester United's next manager