Jason Kelce‘s altercation with an unruly spectator at the Penn State game this weekend is on law enforcement’s radar … with officials looking into the matter.

TMZ Sports has learned … the school’s Police and Public Safety agencies are investigating the viral interaction between the Philadelphia Eagles legend and a man who referred to his brother, Travis, as a homophobic slur … and the process is “ongoing.”

Kelce was in town to catch the massive showdown between Ohio State and Penn State … which the Buckeyes ultimately won by a final score of 20-13.

In the video … one individual is heard directing a question to Jason, saying, “Kelce, how does it feel your brother is a f***** for dating Taylor Swift?”

Kelce lost it … turning around, grabbing someone’s phone and smashing it to the ground.

TMZ Sports obtained additional footage … showing the person shoving Kelce, demanding he give him his phone back — when Kelce shouted three times, “Who is the f***** now?”