LOS ANGELES (Variety.com) - Federal authorities have determined that hackers working on behalf of the North Korean government were behind the attack on Sony Pictures Entertainment, according to CNBC and CNN.

"We have found linkage to the North Korean government," a source told CNBC.

CNN's Evan Perez said that an announcement is expected on Thursday that would "assign attribution" to the country, which threatened retaliation over the release of "The Interview."

An FBI official said that the agency had no immediate comment because the investigation is ongoing. But they are expected to issue a statement on their findings within the next day.

The New York Times reported that U.S. officials had differences of opinion on whether the hackers were aided by Sony insiders.

It's unclear what kind of action the U.S. may take, if any, in response, or whether it would issue any kind of an official statement. The White House had no immediate comment.

In an interview with ABC News on Wednesday, President Obama said that his administration was taking the hacker attack seriously but that "for now my recommendation would be, go to the movies."

Sony announced that it was pulling the movie from release after major theater chains decided not to show it. On Tuesday, the studio said that it was leaving a decision of whether to show the movie to exhibitors. That came after the hackers issued a threat of physical harm and a "9/11" style attack at theaters where the movie was being shown. But an official with the Department of Homeland Security told media outlets that there was "no credible intelligence" showing an active plot.