Sony Pictures Entertainment is exploring the possibility that hackers working on behalf of North Korea, perhaps operating out of China, may be behind a devastating attack that brought the studio’s network to a screeching halt earlier this week, sources familiar with the matter tell Re/code.

The timing of the attack coincides with the imminent release of “The Interview,” a Sony film that depicts a CIA plot to assassinate North Korean leader Kim Jong-Un. The nation’s ever-belligerent state propaganda outlets have threatened “merciless retaliation” against the U.S. and other nations if the film is released.

The film is a comedy and features actors Seth Rogen and James Franco as celebrity journalists who score a rare interview with the North Korean leader, played by the actor Randall Park. In the film, the journalists are enlisted by the CIA to assassinate Kim.

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Sony and outside security consultants are actively exploring the theory that the hack may have been carried out by third parties operating out of China on North Korea’s behalf. The sources stress that a link to North Korea hasn’t been confirmed, but has not been ruled out, either.

The hackers, operating under the name “Guardians of Peace,” or #GOP, left an image bearing a message on the computers screens of Sony employees Monday morning. The message threatened to release sensitive data supposedly stolen from Sony servers if certain demands were not met.

On Wednesday, some of those files were said to have leaked on the Web by way of a thread on Reddit, though their veracity hasn’t been independently confirmed. The attack is said to have locked Sony Pictures employees out of their computers entirely, forcing them to resort to pen and paper to do their jobs.

Sony declined to comment beyond a statement it issued Tuesday: “Sony Pictures Entertainment experienced a system disruption, which we are working diligently to resolve.”

Similarly devastating attacks have been blamed on North Korea in the past. Last year, North Korea was said to have been behind an attack against two South Korean TV broadcast networks as well as its financial system. Employees of the two TV networks were said at the time to be left with blank computer screens. That attack also paralyzed South Korea’s network of ATM machines, preventing people from withdrawing money from their bank accounts.