A district-wide school lockdown has been lifted after a reported threat was found on Internet message boards warning Houston of an imminent attack, according to Houston Local News.

The lockdown took place Friday afternoon, affecting all Spring Branch Independent Schools. During the lockdown, no one was allowed to enter or leave the school buildings.

The alert started after the Houston Regional Intelligence Service Center notified officials of a reported message left on an Internet bulletin board, according to Click2Houston.

"If you live in Houston, get out of school building at 1:30 p.m. I'll be wearing gray sweatpants to school," read the message. "Avoid being in the same room."

The "non-specific threat" caused the schools to go into a brief lockdown, but educators were able to continue their lessons as it progressed.

Police officials wrote in a statement that there were "NO THREATS against any specific school," and that "officers are on heightened alert and closely monitoring all school properties."

The Spring Branch Independent School District released the following statement to parents: "We have now lifted the lockdown under the direction of SBISD Police and campuses have returned to their normal schedules.... Thank you for your cooperation and support as we place the security of our students and staff as our highest priority."