An Air Force academy preparatory school in Colorado went on lockdown late Friday after reports of an active shooter — but officials later determined that there were no shots fired.

“Mil personnel & LE are clearing dorms including knocking on doors to check on cadets on USAFA,” the El Paso Sheriff’s Office tweeted.

“No reported injuries or shots fired.”

Still, as a precaution, residents at the academy, in Colorado Springs, were told by military police to shelter in place after reports of shooting at the campus community center.

All access to the academy was also ordered closed.

The El Paso County Sheriff’s Office tweeted that it was joining with military personnel in investigating — but stressed that “nothing is confirmed yet.”

The academy’s preparatory school, which is near the community center, has been the site of racial strife this week.

On Monday, racial slurs were written on the dormitory white boards outside the rooms of five teenaged black cadet candidates at the school — reading “go home n—-r,” according to the Air Force Times.

The hate messages prompted the school’s superintendent, Lt. Gen. Jay Silveria, to assemble the school’s more than 4,000 cadets and staff for a stern rebuke, the Guardian reported.

“If you can’t treat someone from another race or a different color skin with dignity and respect then you need to get out,” he told them.

“That kind of behavior has no place in the United States Air Force,” Silveria said. “You should be outraged not only as an airman but as a human being.