A White House official said on Monday that the purported leak of sensitive Pentagon documents poses a threat to national security that the U.S. is taking very seriously.

John Kirby, White House National Security Council(NSC) coordinator for strategic communications, made the remarks during a press briefing, saying that the information has no business in the public domain.

Kirby said that the U.S. must protect not only the information, but also the way it was collected, avowing that a thorough investigation into the leak will be conducted and action taken if necessary.

The NSC spokesperson said that some of the documents have been doctored but declined to confirm the validity of the entire leak, adding that the U.S. has not identified the perpetrator or their motive, and it is unclear if there are more documents out there.

Regarding the fact that the leaked documents include content on U.S. allies including South Korea and Israel, Kirby said that the U.S. has been in touch with the relevant partner nations, and the U.S. will keep them as informed as possible.