MENOMONIE, Wis. (WEAU) -- Three people are hurt after a fight outside a fraternity house in Menomonie.

The Menomonie Police Department says it happened around midnight on Sunday at 1120 6th Street E., at the Chi Lambda Fraternity House.

Officers say unknown suspects tried to get into a party at the house, but the suspects were confronted by a resident inside and advised them to leave.

That's when a physical altercation began outside the house in the yard. Officers say three people had minor injuries.

The suspects took off from the scene by foot before officers arrived and have not been found.

Officers say witnesses reported they heard gunfire and saw a muzzle flash during the fight.

But officers say no guns were actually observed by witnesses or recovered by police.

After further investigation, officers found a spent casing along the boulevard near the house.

The description and the number of suspects involved in the fight has not been confirmed at this time.

Investigators say they believe the incident is not gang affiliated or related to the home invasion incident on December 21, 2011.

Anyone with additional information is asked to call Inv. Dave Pellett at the Menomonie Police Department: 715-232-2198.