(AP) — Three middle-school students have been charged with plotting to kill multiple people at their upstate New York school with guns and explosives, authorities said Friday.

The Albion Middle School students were arrested Thursday after investigators determined a threat that started on an online gaming app was credible, Albion Police Chief Roland Nenni said by phone.

The students, all under 16 years old, are charged as juveniles with conspiracy to commit multiple murders, he said. Their names and ages weren’t released.

“They had a date set,” Nenni said. “The plan was to use explosives, incendiary devices and firearms to kill and injure students and staff in the Albion Middle School.”

He said officers recovered electronics and some legally possessed firearms during an investigation that was initiated after a student-on-student threat in the online gaming app Discord, on Monday.

Nenni did not disclose where police searched or where the weapons were located. But Orleans County District Attorney Joseph Cardone said via email that “there is no belief that the students had access to them and they were taken with cooperation of the students’ families.”

The threat also implied a broader danger, Nenni said, leading investigators to activate the school’s threat assessment team and involve multiple local, state and federal agencies. Authorities have not yet identified a possible motive, he said.