Classes have resumed at Cross Timbers Middle School in Grapevine after it was evacuated Tuesday morning because of a bomb threat.
Grapevine police said the threat was reported at about 9:30 a.m.
Students and staff were moved to a safe location nearby while officers searched the school.
They did a full sweep of the building on foot. Then DFW Airport police brought in their bomb-sniffing dogs to go through the school again.
"We want to double-check that there is nothing in the building," said Amanda McNew, spokesperson for the Grapevine Police Dept. "That it is completely safe for everyone to go back inside."[[559260452,C]]
Nothing was found and officers determined the building was safe about two hours later at noon.
Police said the investigation now turns to who made the threat.
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"We'll be looking at the call that came in, listening to the voice -- gathering any information we can get from it," said McNew. "Making a school threat is a crime. And if we are able to identify the person we would absolutely pursue criminal charges."
NBC 5's Tim Ciesco and Holley Ford contributed to this report.
