Two teenage girls are in custody after allegedly threatening to place pipe bombs in a Montgomery County, Texas, high school, and opening fire on the students, according to police.

Spring Branch ISD police told Fox News that the two teenage girls, ages 15 and 16, were going to place pipe bombs at Memorial High School before shooting the students.

The 16-year-old girl, police said, attends the school and was found there about 30 minutes after the threat was made.

The threats were reportedly communicated on social media and were extremely detailed, which is what led police to believe the threat was credible.

“FBI Houston received information yesterday that two underage teenagers from the Houston area were plotting a mass casualty attack at a local school,” the agency wrote on X. “Our Threat Mitigation Team immediately responded to help [Houston Police] and [the Montgomery County Sheriff’s Office] identify and arrest them.”

The Montgomery County Sheriff’s Office is investigating the case and noted that the students attended different high schools.

The sheriff’s office also said one of the individuals was in custody on unrelated charges, while the other was taken into custody in Harris County.

“The safety and security of our schools and community remain our highest priority. We understand the concerns this situation may cause for students, parents, and faculty, and we are taking every necessary precaution,” the sheriff’s office said. “Additional security measures have been implemented, and we continue to work closely with school officials and our law enforcement partners to ensure a safe environment.”