A lockdown at Etiwanda High School in Rancho Cucamonga was lifted following a "reported safety threat" Monday morning.
Etiwanda School District tweeted about the lockdown around 9 a.m.
Chaffey District Superintendent Mat Holton said Rancho Cucamonga sheriff's deputies received a bomb threat over the phone. The school was placed on lockdown while authorities searched the campus.
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Deputies found nothing suspicious on campus and the lockdown was lifted a short time later.