WASHINGTON (AP) — The Pentagon says online leaks of scores of highly classified documents about the Ukraine war present a “very serious” risk to national security and senior leaders are quickly taking steps to mitigate the damage.

In the days since Defense Secretary Lloyd Austin became aware of the leaks, he’s reached out to top allies, convened daily meetings to assess the damage and set up a group not only to assess the scope of the information lost but review who has access to those briefings.

And as the public airing of the data sends shockwaves across the U.S. government, the White House says there are concerns there could be additional leaks.