Five community colleges in the Denver area were closed or locked out after threats were made against them.

Police later said the email threat received by some individuals at the colleges early Friday morning was a hoax and “a form of doxing.”

Colorado Community College System officials say threats have been made against Arapahoe Community College, Community College of Aurora, Community College of Denver, Front Range Community College and Red Rocks Community College.

Community College of Aurora was placed on lockout, which is when classroom teaching continues, but campus buildings and grounds are secured.

The other colleges were closed for one day.

In addition, the University of Colorado Boulder said that while there was no threat to the campus, all classes and activities were canceled as a precaution. CU Colorado Springs said it was also closed for the day.

“We are working closely with campus security teams and law enforcement agencies to monitor the situation,” Colorado Community College System officials said.

“Some colleges currently have a lockout protocol; we encourage students, faculty and staff to check their institution’s website for campus-specific information.”

Police in Westminster, Colorado, say officers contacted a person of interest on Friday and that “it appears the threats are some form of doxing against this person.”