The DEA continues to assist the New Haven police with the arrests, and into the investigation on how the mass-overdose happened.
Many patients were treated by EMS and some were taken to local hospitals, while others refused to be transported, officials said. Hawk said some people got better with the help of naloxone, an opioid overdose reversal drug, while others didn't. "It's a nationwide problem that people are self-medicating for several different reasons, and every agency - police, fire, medical hospitals - all are strained at this time".
"Two individuals had life-threatening symptoms, and the others had non-life-threatening symptoms", he said.
Officials have arrested a 37-year-old man, Felix Melendez, in connection with the overdoses, according to the New Haven Register.
The overdoses were initially feared to stem from a batch of synthetic marijuana, also known as K2 or Spice, possibly laced with an opioid. Some people who overdosed returned to the green and overdosed again, officials said.
Authorities said 19 more people overdosed Thursday, and that the number could climb.
In two cases, Narcan was not effective in the field, but a high dose of Narcan at the hospital was effective in combating the overdose effects.
On Thursday, police suspected the batch of K2, or synthetic marijuana, was still circulating through the area.
The Office of Emergency Management in New Haven said it is still fielding calls and the number of victims could increase.
An ambulance crew responds to one of three simultaneous drug overdose victims. The city also saw more than a dozen synthetic marijuana overdoses in late January.
Officials said the blood of Wednesday's victims was being tested to see what exactly they ingested.
"The substance behind these overdoses is highly unsafe and must be avoided", Malloy said, adding that state public health officials had delivered 50 doses of Naloxone to New Haven to replenish the supply expended by first responders over the course of the 24-hour crisis.
"Today's emergency is deeply troubling and illustrative of the very real and serious threat that illicit street drugs pose to health of individuals", Malloy said. They say no deaths have been reported so far, but at least six victims were near death.
The AP notes, "New Haven first responders were called to a similar overdose outbreak on the Green on July 4, when more than a dozen people were sick from synthetic marijuana".
NBC News reported that the Yale-New Haven Hospital received seven patients and some were in critical condition.
"We want people to be warned that what they have could be extremely risky and they should not use it", he said.