In about 12 hours Wednesday, more than 30 people - most of whom had been on the New Haven green - were treated for overdoses of a drug known as "K2" laced a with a synthetic opioid, police said.
"The man was arrested within the last hour by members of the NHPD Intelligence Unit", police said in a release.
He said authorities have been treating and sometimes transporting six or seven people at one time and the actions of first responders have been "lifesaving".
This isn't the first time the city has seen a mass-overdose: A New Haven man pleaded guilty to charges in connection with overdoses of more than a dozen people in June 2016.
"Even while we were trying to return people to service, they were passing victims on the ground", Alston said.
"We heard from people on the Green this morning that it could potentially be laced with PCP and some of the reactions of the patients in the emergency department would suggest it was an opioid involved as well", Bogucki said.
Police say there haven't been any deaths linked to the overdoses, although two people were hospitalized in critical condition.
Thursday, Emergency Operations Director Rick Fontana said that only a few required admittance to the hospital, with more people being discharged or leaving before any treatment.
Early reports indicated that 47 people had overdosed, but The Hartford Courant reports that the number of cases had risen to 71 by about 10 p.m. Wednesday.
A new report estimated a record 72,000 Americans died previous year from drug overdoses, a rise of around 10 percent, the Centres for Disease Control said on Wednesday. "We have no deaths reported".
"We're getting another call", Alston told reporters, some of whom began chasing after medical workers as they rushed to treat the affected person. Other reports said it was 76 people. Fire and emergency crews responded to an area right across from City Hall.
In October, Donald Trump labelled America's opioid epidemic a "public health emergency", giving officials extra powers to tackle the crisis. 'Narcan was not effective here at the scene, ' said Alston.
New Haven emergency personnel respond to overdose cases on the New Haven Green in Conn.on August 15, 2018.