COLLEYVILLE Colleyville Heritage Elementary, Middle, and High Schools were locked down Tuesday afternoon after a student found an "anonymous note" in the high school cafeteria and reported it to the front office.
"It contained a very vague threat against Colleyville Heritage," said high school Principal Joe Harrington in an e-mail dispatched to parents.
Harrington initially told parents that the note was not believed to represent a credible threat.
"At 2:54 pm we made the decision to place the school in lockdown as a safety precaution," Harrington wrote in a subsequent e-mail. "A student reported additional information concerning the anonymous threat that was found at lunch."
The middle school dismissed students at its normal time, 3:25 p.m., while a police presence remained outside the adjacent high school.
Grapevine Colleyville Independent School District spokeswoman Megan Overstreet said she expected the high school to let out around 4 p.m.
Colleyville police are investigating.