Police have commenced an investigation into the aggressive behaviour of fans at a football game in western Sydney yesterday.

Around 6.30pm (Saturday 25 April 2015), a flare was let off in the northern stand of Pirtek Stadium, Parramatta, during an A-League Game involving the Western Sydney Wanderers and Perth Glory.

Police identified the man responsible for lighting the flare and, with the assistance of stadium security, attempted to approach the man.

A number of people who were standing near the man surrounded police and security, shouting at the officers in an aggressive manner. Police were forced to use OC spray and further officers were deployed in to the stand.

The man believed to be responsible for letting off the flare was apprehended, removed from the stadium and his details were taken. He was also banned from the stadium.

Five people in the crowd were subsequently treated for OC exposure. No one was taken to hospital.

At half time, a number of fans left the game, congregating outside the northern end of the stadium.

Some members of the group, believed to number approximately 150 people, threw cigarettes and coins at police, while others approached officers in an aggressive manner. Police were again forced to use OC spray before back-up from the Public Order and Riot Squad and Dog Squad arrived and the crowd dispersed.

Two male senior constables were treated for minor injuries after one of them had a coin thrown into his face and the other was kicked and punched in the back.

Inquiries into the matter are now underway and police from Parramatta Local Area Command will work with stadium staff and club officials to track down those responsible for the anti-social behaviour.