(CNN)A 13-year-old boy who was found unconscious after a presumed fentanyl exposure at his Hartford, Connecticut, school last week has died, police said.
The boy died Saturday at approximately 5:35 p.m. Two other male students who were also taken to a nearby hospital on Thursday were later released, police said in a news release.
The 13-year-old, who collapsed in gym class, had ingested fentanyl, Hartford Mayor Luke Bronin said Thursday.
The city "grieves for this child lost, for his loved ones, his friends, his teachers" and the entire community at his school, Bronin said in a statement over the weekend.
"We still have much to learn about the circumstances of this tragedy, and about how a child had access to such a shocking quantity of such deadly drugs, and our police (department) will continue their investigation and seek to hold accountable the adults who ultimately are responsible for this child's death," Bronin said.
The rest of the students at the school, the Sport and Medical Sciences Academy, were placed under a "code yellow," which is a shelter in place order, after the incident Thursday. Multiple agencies and drug sniffing dogs carried out a check for other narcotics before students were let go for the day, the police said.
The drugs were believed to have been brought to the school by a student, Bronin said. During the sweep "there were multiple additional bags, of what we believe was fentanyl, found around the school."
Students and faculty had to have their shoes decontaminated in case they contained trace amounts of the presumed drug. Everyone in the facility "had to walk through a solution of bleach and OxiClean which dissolves and neutralizes the fentanyl before they were allowed to leave the building," police Chief Jason Thody said.
Fentanyl can be a threat to anyone who comes into contact with it. It can be absorbed through the skin or accidentally inhaled, and just a quarter of a milligram can be lethal.
According to its website, the academy is a magnet middle and high school, "with a focus on sport and medical sciences." CNN affiliate WFSB said the school has approximately 600 students.
The school was closed Friday for a full cleaning of the campus, which was expected to take several days, Principal Alison Giuliano said in a letter to parents. Parents are expected to be updated Monday, a school holiday, about when classes will resume. Support services are available to students who need them, she said.