Two people were said to be in a life-threatening condition. Officials weren't certain whether Thursday's cases involved the same batch of "K2" synthetic marijuana.
Most were treated at local hospitals, though at least five refused to be transported.
Synthetic cannabinoids like K2 are human-made chemicals that can be either sprayed on dried plants and smoked or sold as liquids to be inhaled in e-cigarettes or other devices. It has been blamed for overdoses globally.
Some of the New Haven victims tested positive for the powerful opioid fentanyl, also blamed for overdoses, but authorities believe this week's overdoses were caused exclusively by synthetic marijuana.
Police said they arrested a man believed to be connected to at least some of the overdoses. The names of the suspects haven't been released.
"Better education, more resources, definitely it will be getting a lot more attention from a law enforcement standpoint, of course, resources like Narcan which we had brought in, being able to have Narcan possibly stationed on the green, so we can have a faster response", Campbell said. "Someone. with malice in their heart took advantage of that, took advantage of this vulnerable population".
"Whoever is doing it, is doing it on objective, handing it out for free, not even buying it, bad intentions from the start", Rodriguez said.
The New Haven Police Department is investigating the case. He said that in addition to state charges, the suspects could also face federal charges.
Mayor Toni Harp said plans were being finalized for President Trump's drug czar nominee, Jim Carroll, to visit New Haven on Monday.
"This is happening nationwide", Harp said. The additives boost the high, but can create a unsafe, sometimes deadly cocktail.
Investigators were still trying to determine what exactly sickened the victims. Toxicology tests remained pending.
Paramedics sprinted from patient to patient in a park overlooked by Yale University buildings as users began to show symptoms including vomiting, hallucination and unconsciousness.
Gov. Dannel Malloy said Wednesday that the state Department of Public Health and the Department of Mental Health and Addiction Services were assisting New Haven with the rash of overdoses.
An official in the city said earlier there were a total of 25 overdoses over a three-hour span and that some overdoses were "in multiples of 4-6 at a time". Three more overdoses were reported at the Green Tuesday night, but officials could not confirm whether they were related. No deaths were reported in either outbreak.
"I just don't understand why you would keep purchasing this stuff that's laced, your life is at risk, not a smart thing to do", said Ahisamac Rodriguez, of New Haven.