Officials at the U.S. Federal Bureau of Investigation (Fbi) released a warning on Tuesday (16Dec14) advising theater bosses they could be the next target of a hack attack if they screened Seth Rogen and James Franco's controversial film The Interview.

A group of activists infiltrated Sony Pictures' database last month (Nov14), and sent out a message threatening 9/11-style attacks on any cinema screening the comedy, which features two Americans who set out on a mission to assassinate North Korean leader Kim Jong-un.

Chiefs at five major movie theater chains announced on Wednesday (17Dec14) that they would not be screening the film, and soon after, bosses at Sony Pictures made the unprecedented decision to scrap the film all together and cancel its scheduled release date of Christmas Day (25Dec14).

Now a private document has been obtained by Reuters, showing Fbi officials warned cinemas bosses and other businesses associated with The Interview that they could be the next ones targeted in the cyber attacks.

The Fbi has been investigating the case, and according to a statement from the National Security Council spokeswoman Bernadette Meehan, the U.S. government is "working tirelessly to bring the perpetrators of this attack to justice, and we are considering a range of options in weighing a potential response".

She adds, "The U.S. government has offered Sony Pictures Entertainment support and assistance in response to the attack... The United States respects artists' and entertainers' right to produce and distribute content of their choosing. The U.S. government has no involvement in such decisions. We take very seriously any attempt to threaten or limit artists' freedom of speech or of expression."

During an interview with ABC News on Wednesday, U.S. President Barack Obama reiterated that they have taken the situation seriously, and urged folks not to be thwarted by the threats and continue going to the cinema over the holidays.

He said, "Well, the cyberattack is very serious. We're investigating it. We're taking it seriously. You know, we'll be vigilant. If we see something that we think is serious and credible, then we'll alert the public. But for now, my recommendation would be that people go to the movies."