Two 14-year-olds have been accused of calling in a false report of an active shooter at Matthew Henson Middle School in Charles County, Maryland, on Tuesday morning.

The teens, who are students at Matthew Henson, used another student’s phone to call in the false report just before 10 a.m., the Charles County Sheriff’s Office said in a statement Wednesday.

The report caused a lockdown at Matthew Henson Middle School and a lock-in at J.C. Parks Elementary School nearby.

Investigators determined that the call, which came from inside the school, was false and that there wasn’t an active threat. Both schools were cleared to resume normal activities about a half-hour later.

“We take this extremely seriously,” Katie O’Malley Simpson, director of communications for Charles County schools, told WTOP. “Filing a false report can result in a range of school action disciplines up to a school expulsion.”

The teens could face up to six months of incarceration and up to a $500 fine, the sheriff’s office said.

WTOP’s Megan Cloherty contributed to this report.