JONESBORO, Ark. (TheBlaze/AP) — Arkansas State University has lifted a lockdown of its Jonesboro campus that followed reports of armed men near the student union.

The university lifted the lockdown about an hour after it took effect after school and city police determined there was no threat.

The university sent an emergency alert shortly before 2 p.m. Sunday saying two armed men were seen near the student union. A later message said three men wearing all black were seen.

Campus lockdown has been lifted at Arkansas State. Investigation continues. pic.twitter.com/3v2GwF8oAe

— Diana Davis (@davis_diana) February 14, 2016

University police and area law enforcement were clearing campus buildings, the school's website said before the lockdown was lifted.

Here's another photo @EvanCaddy just tweeted. Appears to be police officers in tactical gear. #ARnews pic.twitter.com/BeoCPf9BeV

— Mitchell McCoy (@MitchellMcCoy) February 14, 2016

A pair of students sent out the following tweets during the situation:

JUST HAD TO SPRINT FROM THE UNION!! THERE ARE PEOPLE WITH GUNS AGAIN SO EVERYONE BE SAFE!!!!!

— Han (@HannahRose30)

February 14, 2016

EVERYONE ON ASU CAMPUS STAY IN YOUR ROOMS AND GET SOMEWHERE SAFE THERE ARE PEOPLE DRESSED IN BLACK WITH GUNS

— Hannah Dickey (@lildickeyy) February 14, 2016

Neither ASU nor Jonesboro police immediately returned phone calls seeking comment.

The lockdown was the second at the school in the last three months.

A man with a shotgun drove onto campus on Dec. 10. That incident ended peacefully as the man eventually surrendered.

This story has been updated.