Two teenagers are under arrest for allegedly plotting what the FBI is calling "a mass casualty attack" at a Houston-area high school.

Two teenagers are under arrest for allegedly plotting "a mass casualty attack" at a Houston-area high school, the FBI said Wednesday night. The teen girls were accused of threatening to place pipe bombs and shoot their peers,

Evidence suggests their intent was to carry out acts of violence at a school in the Spring Branch Independent School District, law enforcement said.