Grey Culbreth Middle School closed Tuesday morning after malfunctioning electrical equipment in the cafeteria sent smoke into hallways, officials said.
The equipment was part of the refrigeration system, Chapel Hill Carrboro City Schools spokesman Jeff Nash said.
Parents were told they could pick up their children as soon as the school closed, about 9 a.m.
Nash said buses would arrive at the school at 10:30 a.m. to take home students who had not been picked up.
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Maintenance workers were determining the extent of the damage, Nash said.