City officials in New Haven declared a state of emergency on June 23 after a batch of tainted heroin led to nearly 20 overdoses, including several fatalities.

Though initial reports from the New Haven Police Department indicated that there were 15 confirmed overdoses and two fatalities, those numbers have risen to 17 overdoses and three fatalities, according to a press release from the office of Connecticut Sen. Chris Murphy. Four people remain hospitalized.

Three men were arrested and charged with possession with intent to distribute and distribution of controlled substances in conjunction with the overdoses, including Steven Whaley, 48, a night custodian at Lincoln-Bassett School. Whaley, who had “very minimal contact” with students, has been placed on unpaid administrative leave, according to a Wednesday press release from the New Haven School District.

“At this time, there are no indications that students have had any exposure to this incident and we will continue to ensure all students within our school walls have a safe educational environment,” the release said.

Whaley and the two other men remain in custody.

The batch of heroin was believed to be laced with fentanyl, a synthetic opioid that is up to 50 times more potent than heroin, according to the police. It can be ingested through the skin and, if taken in high enough doses, cause respiratory failure, according to the Center for Disease Control’s website.

New Haven is not the first city in Connecticut to be affected by fentanyl: according to data released by state medical examiner James Gill in May, there were 83 fentanyl-related deaths in the state during the first three months of 2016.

It is possible to reverse an overdose with the opiate anti-overdose drug naxolone, also known by its brand name Narcan, but due to amount of Narcan required to treat a fentanyl overdose and the high number of cases reported in New Haven last week, the drug’s supply was dangerously low, said Assistant Fire Chief Matthew Marcarelli.

As a result, the state Department of Public Health sent 700 doses of Narcan to New Haven on Friday, June 24.

The press release from Murphy’s office also noted that Murphy, fellow Connecticut Sen. Richard Blumenthal LAW ’73 and Congresswoman Rosa DeLauro are working with Congress to pass emergency federal funding. The three congresspeople will meet with NHPD Chief Dean Esserman and other first responders at the Police Department on Friday.