NEW YORK » Hackers calling themselves Guardians of Peace made ominous threats Tuesday against movie theaters showing Sony Pictures’ film "The Interview" that referred to the terrorist attacks of September 11, 2001. The group also released a trove of data files including about 8,000 emails from the inbox of Sony Entertainment CEO Michael Lynton.

The data dump was what the hackers called the beginning of a "Christmas gift." But GOP, as the group is known, included a message warning that people should stay away from places where "The Interview" will be shown, including an upcoming premiere. Invoking 9/11, it urged people to leave their homes if located near theaters showing the film.

The Department of Homeland Security said there was "no credible intelligence to indicate an active plot against movie theaters," but noted it was still analyzing the GOP messages. The warning did prompt law enforcement in New York and Los Angeles to address measures to ramp up security.

"The Interview" is a comedy in which Seth Rogen and James Franco star as television journalists involved in a CIA plot to assassinate North Korean leader Kim Jong Un. Its New York premiere is scheduled for Thursday at Manhattan’s Landmark Sunshine, and is expected to hit theaters nationwide on Christmas Day. It premiered in Los Angeles last week.

Rogen and Franco pulled out of all media appearances Tuesday, canceling a Buzzfeed Q&A and Rogen’s planned guest spot Thursday on "Late Night With Seth Meyers." The two stars had just appeared Monday on "Good Morning America" and Rogen guested on "The Colbert Report." A representative for Rogen said he had no comment. A spokeswoman for Franco didn’t respond to queries Tuesday.

The thousands of documents leaked Tuesday included banal emails about public appearances, dinner invitations and business introductions. But they also included information about casting decisions for upcoming films and sensitive corporate financial records, such as royalties from iTunes, Spotify and Pandora music services.

The FBI said it is aware of the threats and "continues to work collaboratively with our partners to investigate this matter." It declined to comment on whether North Korea or another country was behind the attack. Speculation about a North Korean link to the Sony hacking has centered on that country’s angry denunciation of the film. Over the summer, North Korea warned that the film’s release would be an "act of war that we will never tolerate." It said the U.S. will face "merciless" retaliation.

The New York Police Department, after coordinating with the FBI and Sony, plans to beef up security at the Manhattan premiere, said John Miller, the NYPD’s top counterterrorism official.

"Having read through the threat material myself, it’s actually not crystal clear whether it’s a cyber response that they are threatening or whether it’s a physical attack," Miller said. "That’s why we’re continuing to evaluate the language of it, and also the source of it. I think our primary posture is going to be is going to have a police presence and a response capability that will reassure people who may have heard about this and have concerns."

Following a commission meeting earlier Tuesday, Los Angeles Police Chief Charlie Beck said his department takes the hackers’ threats "very seriously" and will be taking extra precautions during the holidays at theaters. Patrick Corcoran, spokesman for the National Association of Theater Owners, wouldn’t comment on the threats.

In their warning Tuesday, the hackers suggested Sony employees make contact via several disposable email addresses ending in yopmail.com. Frenchman Frederic Leroy, who started up the yopmail site in 2004, was surprised to learn the Sony hackers were using yopmail addresses. He said there was no way he could identify the users.

"I cannot see the identities of people using the address … there is no name, no first name," he said in a phone interview with The Associated Press. He said yopmail is used around the world but there are "hundreds and hundreds" of other disposable email sites.

Leroy, who lives in Barr, outside Strasbourg in eastern France, said he heard about the Sony hackers yesterday on the radio but knows nothing more. He said he has not been contacted by any authorities.

Since Sony Pictures was hacked by GOP late last month in one of the largest data breaches ever against an American company, everything from financial figures to salacious emails between top Sony executives has been dumped online.

Separately Tuesday, two former Sony film production workers sued Sony Pictures Entertainment over the data breach. They alleged the Culver City, California company waited too long to notify employees that data such as Social Security numbers, salaries and medical records had been stolen.

The filing comes one day after two other former Sony employees filed a suit accusing the company of negligence in not bolstering its defenses against hackers before the attack. It claims emails and other information leaked by the hackers show that Sony’s information-technology department and its top lawyer believed its security system was vulnerable to attack, but that company did not act on those warnings.

Both cases seek class-action status to represent current and former Sony employees whose private data was posted online.

Sony has not responded to phone calls for comments about the hacker threat and the suit.