Philadelphia Police are warning Eagles fans not to mess with New Orleans Saints fans during Saturday’s wild-card playoff game. That’s because those dressed in Saints gear might not be fans at all, they may just be an undercover officer.

Third District Community Policing Officer Mike Duffy sent out a warning on Twitter late Thursday night about the Saints patrol:

It’s well documented that Philadelphia fans have a long history of treating both fans of opposing teams and their local brethren poorly.

In 2012, following the Winter Classic, a man wearing a New York Ranger jersey was allegedly beaten by a Flyers fan outside Geno’s Steaks. A man was also killed in 2009 following a fight in a parking lot outside Citizens Bank Park.

The now-defunct Veterans Stadium used to have “Eagles Court,” in which a Philadelphia Municipal Court judge presided over unruly fans who had been arrested during games.

Outside of Philadelphia, a brawl between three New England Patriots fans and a New York Jets fan at MetLife Stadium in Oct. 2013 led to four arrests.

Tickets for Saturday's primetime game sold out in three minutes earlier this week, with seats being sold on secondary ticketing sites like StubHub for thousands of dollars.

The Philadelphia Eagles Fan Code of Conduct prohibits “fighting, taunting or threatening remarks or gestures” as well as abusive or foul language, among other things. The policy, which is clearly displayed and shared at Lincoln Financial Field, says violators will be ejected or arrested.

Philadelphia Police spokesman Lt. John Stanford said on Friday that the department has deployed plainclothes officers, as well as uniformed patrols, at Eagles games for the past several years. He says some officers wear the opposing team's jersey, others wear Eagles gear and some wear neither.

"We do it just to make sure that people can go out and have a good time," he said. Stanford added that the patrols are not meant to target one group of fans, but to prevent trouble.

Duffy’s announcement drew support and ire from followers. One man, named Jesse, called the move “terrible.”

Another follower supported the initiative, calling it "smart policing."

Contact Vince Lattanzio at 610.668.5532, vince.lattanzio@nbcuni.com or follow @VinceLattanzio on Twitter.