Defense Secretary Lloyd Austin said Tuesday that the U.S. will “turn over every rock” to find the source of the apparent leak of dozens of highly classified documents on the internet in his first public comments since the documents came to light, writes ABC News.

More apparently leaked documents continued to emerge on Monday as The Washington Post reported on documents it says it obtained that appear to raise concerns that Ukraine’s upcoming spring offensive will only be moderately successful and that Egypt’s leader had secretly directed that his country provide Russia with thousands of rockets.

“We take this very seriously and we will continue to investigate and turn over every rock until we find the source of this and the extent of it”, Austin told reporters at a State Department press conference.

He said that he was first informed of the apparent leak the morning on April 6 after some of the documents were posted on popular social media platforms. He said that since then he has been leading daily meetings with top officials to coordinate a response to the leak and directed “an urgent cross-department effort”.

Austin said he was limited in what he could say because of the ongoing Justice Department criminal investigation into the leak but he provided new details that investigators are focused on documents dated Feb. 28 and March 1.

“I don’t know if there are other documents that have been online before. These are things that we will find out as we continue to investigate. They were somewhere in the web and where exactly and who had access at that point, we don’t know, we simply don’t know at this point”, - he said.