Two Burleson high schools were placed on lock down Monday after a former student threatened a current student, police and school officials say.

Burleson city officials said Burleson and Centennial high schools were locked down for much fot he day as a precaution after a former Centennial High School student made a vague threat on Facebook toward a current student of the district.

"The Burleson Police Department has advised us that they are currently working with the Granbury Police Department to locate a former student who made a vague threat, via social media, to a current student," the district said in a news release. "In an abundance of caution, both of our high schools are in standby lock down until we receive notice from police officials that the situation has been resolved. Campuses will remain closed to outside visitors for the time being."

With the threat involving Centennial High School, officials have not said why Burleson High School is also locked down.

Just after 3 p.m., the district said the lockdowns had been lifted and that the campuses have resumed normal operations and that all activities planned for the afternoon and evening would proceed on schedule.

District officials, meanwhile, said they will continue working with police to investigate the threat against the district's student.

"Please know that students are safe here at school, security is tight, and we will continue to keep you up to date," school officials stated. "Police have requested that parents refrain from coming to the campus in order to allow them to best maintain a secure environment."