WARWICK — The cause of death for Justina Steffy, the 31-year-old woman whose remains were found in Warwick in October, has been deemed homicide.

Steffy’s death certificate, which was modified Jan. 29, identifies the immediate cause of her death as the “combined toxic effects of fentanyl, 4-ANPP and xylazine.”

According to the U.S. Drug Enforcement Administration, 4-ANPP is a precursor to fentanyl and is often used in illicit manufacturing of the opioid. Xylazine, also known as “Tranq,” is a sedative that, according to the DEA, is often mixed into illicit fentanyl.

Although her death certificate lists her place of residence as Weare, New Hampshire, Keene Police reported Steffy missing from Keene in early October.

When contacted this week, Keene Police Detective Joel Chidester referred questions to New Hampshire Attorney General’s Office spokesperson Michael Garrity.

“The New Hampshire Attorney General’s Office has been and is working with the Keene Police Department to investigate Ms. Steffy’s death,” Garrity wrote in an email Tuesday. “From that investigation, there is no danger to the public, but there is no further information to share at this time.”

A portion of Hastings Heights Road in Warwick was closed from approximately 7 p.m. on Tuesday, Oct. 22, until noon the next day as both Massachusetts and New Hampshire law enforcement searched for Steffy, whose identity was made public by Keene Police on Oct. 31.

Hastings Heights Road residents reported seeing ambulances and both state and local law enforcement vehicles. On Friday, Nov. 1, a resident who lives at the base of Hastings Heights Road said she saw two state vehicles, one marked “medical examiner,” driving up the road while she was on a walk Wednesday, Oct. 23.

In a public safety alert published by the DEA in 2023, the agency warned the public of an uptick in the trafficking of fentanyl mixed with xylazine.

“Xylazine and fentanyl drug mixtures place users at a higher risk of suffering a fatal drug poisoning. Because xylazine is not an opioid, naloxone (Narcan) does not reverse its effects,” the DEA wrote. “Still, experts always recommend administering naloxone if someone might be suffering a drug poisoning.”