Terre Haute South Vigo High School is on a lockout, the Vigo County School Corp. announced at 12:40 p.m. today.
"We received an unverified phone call threat. We have heightened security on campus and are acting out of an abundance of caution," said Bill Riley, VCSC director of communications.
The numbers were traced and are out of state, he said.
He added, "Everything is safe and school business is happening as normal."
Lockout means all students have been brought inside and no visitors are allowed.
"We received [two] very vague, incomplete phone calls" that prompted the lockout, as a precaution, he said. The calls went to the main office.
He could not provide details about the nature of the calls.
"We believe any threat is coming from outside the building," he said.
Terre Haute police are investigating.
The Tribune-Star will provide more information as it becomes available.