COLORADO SPRINGS, Colo. – The U.S. Air Force Academy has reopened after an 'active shooter situation' Friday at an on-campus residence hall.

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The USAFA sent out an alert late Friday night.

"AN ACTIVE SHOOTER HAS BEEN DECLARED BY LAW ENFORCEMENT. LOCKDOWN. LOCKDOWN. LOCKDOWN," the alert said.

According to KOAA, NBC's Colorado Springs affiliate, roads leading to the Academy were closed until the early hours of Saturday morning, when police gave the all-clear.

All clear: The incident has concluded. There are no confirmed shots fired & no injuries. Everyone is safe. — U.S. Air Force Academy (@AF_Academy) September 30, 2017

Police said they did not find any victims or shooters during a campus sweep.

An investigation is ongoing.

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