While there have been no threats locally, Philadelphia police are on alert at screenings for the new movie Joker amid concerns that showings could be linked to violence.

“We have not received any threats, but will continue to monitor and work with our law enforcement partners in reference to this event,” Officer Miguel Torres said. “We will continue to be vigilant and respond to situations as need arises.”

Released Friday, the film tells a gritty origin story of Batman’s arch-enemy, the Joker (played by Joaquin Phoenix). The film presents him as a mentally ill loner who pursues a life of violent crime after failing to find fame as a stand-up comedian.

“It’s not so easy to dismiss Phoenix’s creepy turn here, pulling the viewer along as he makes the journey from victim to victimizer, a killer who stages media-ready murder spectacles meant to stand as a perverse public monument to his isolation and pain,” Inquirer film critic Gary Thompson wrote in his review. “The kind of guy, in other words, whom we see in the paper every month, taking a rifle to concerts, malls, and movie theaters. Joker can be seen as a sincere attempt to understand such men. And they need to be understood so they can be stopped — I’m not sure they need an origin story, certainly not one that ends as repulsively as Joker.”

The Joker character is linked to a 2012 mass shooting in a theater in Aurora, Colo., in which a gunman killed 12 people and injured 70 during a screening of The Dark Knight Rises. Following the shooting, word that the shooter, James Holmes, referred to himself as the Joker began to spread, but that has since been debunked.

“It never happened,” George Brauchler, a Colorado district attorney involved in the case, recently told Vanity Fair, adding that the idea that Holmes was inspired by the character “has no connection to reality.”

Last month, families of Aurora shooting victims sent a letter to Warner Bros. expressing their concerns over the film. While they said they did not expect the studio to halt release of Joker, they asked that the studio “end political contributions to candidates who take money from the NRA and vote against gun reform,” and “use your political clout and leverage in Congress to actively lobby for gun reform. Keeping everyone safe should be a top corporate priority for Warner Bros.,” according to a copy of the letter obtained by the Hollywood Reporter.

CNN reported that the FBI and Department of Homeland Security this week issued a Joint Intelligence Bulletin warning of threats posted on social media dating back to May. However, the memo reportedly noted, those messages provided no “specific or credible threats to particular locations or venues.”

In response to potential violence, police departments around the country have said they are monitoring the situation closely. According to the New York Post, the New York Police Department has increased security at theaters showing the movie. Chicago police, the Chicago Tribune reported, are working to monitor Joker screenings. In Huntington Beach, Calif., a theater was closed following what police said was a credible threat, the Los Angeles Times reports.

Movie chain Landmark Theatres has reportedly banned costumes during Joker’s theatrical run, with CEO Ted Mundorff telling the Reporter that the company wants “customers to be comfortable in their surroundings.”

Box office analysts expect Joker to pull in $80 million during its opening weekend, Reuters reported.

“Make no mistake: neither the fiction character Joker, nor the film, is an endorsement of real-world violence of any kind,” Warner Bros. said in a statement. “It is not the intention of the film, the filmmakers, or the studio to hold this character up as a hero.”