(Reuters) - A lockdown triggered by a bomb threat at a Roanoke, Virginia, high school on Thursday was lifted after authorities had told students and staff to take shelter, the school district said.

The threat against Northside High School was not credible, a spokesman for the Roanoke County Public Schools said in a statement. The incident is under investigation, he said.

(Reporting by Ian Simpson; Editing by Bernadette Baum)