U.S. investigators are considering multiple suspects, including North Korea, in their investigation into a cyberattack on Sony Pictures Entertainment that knocked out the company's computer systems for over a week, according to a U.S. national security official with knowledge of the investigation.

The official, who asked to remain anonymous, told Reuters on Tuesday that the forensic investigation is in its early stages, and that no clear suspects have emerged.

But the official said multiple suspects are being assessed, including the North Korean government, other nations and private parties.