Medics in News Haven, Conn., responded to more than 70 drug overdoses related to the drug K2 on Wednesday, officials said.

As of Wednesday evening, 71 people had overdosed across New Haven, city spokesperson Laurence Grotheer tells TIME. Police arrested a person of interest in the case on unrelated charges, he says.

Most of the overdoses occurred on the New Haven Green – not far from the campus of Yale University – starting Wednesday morning, Grotheer said.

New Haven fire chief John Alston said at a press conference on Wednesday that emergency responders received calls just after 8 a.m. reporting multiple individuals experiencing overdose symptoms, including unconsciousness, vomiting and nausea. After responding to six reports, Alston said he realized it was a “multi-casualty” incident.

Grotheer said testing by the federal Drug Enforcement Administration found that people overdosed on unadulterated K2, a synthetic marijuana that contains a variety of chemicals and has been linked to prior large-scale overdoses. The K2 was not laced with opioids, Grotheer said.

Patients were taken to the Yale-New Haven Hospital and the Hospital of Saint Raphael.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Mahita Gajanan at mahita.gajanan@time.com.