YES Prep Northline Secondary School was placed on a temporary hold on Wednesday as HPD responded to a safety concern on campus, officials said.
Since the arrest of the teenage girls on Tuesday, investigators have been working to get a search warrant signed by a judge.
The police chief says the teens communicated on social media to plan the attack, and those communications were intercepted by the FBI.
The FBI says the plot involved pipe bombs and guns. The case spans two counties, with the girls attending two different Houston-area school districts.
An Indiana high school student has been accused of plotting a mass shooting at a school near Indianapolis on Valentine's Day, local police said Thursday.