President Donald Trump disclosed “highly classified information” during a meeting with Russian officials last week, according to The Washington Post.

The revelations raise new questions about the already controversial meeting of Trump, Russian Foreign Minister Sergei Lavrov and Sergey Kislyak, who is the Russian ambassador to the U.S. While such a disclosure is likely not illegal, it raises concerns about both the consequences of Trump’s ad hoc style when interacting with foreign leaders and U.S. coordination with other nations on sensitive foreign policy issues.

Trump revealed information to the Russian visitors that “jeopardized a critical source of intelligence on the Islamic State,” the Post reported Monday, citing current and former U.S. officials with ties to the administration. The publication did not elaborate on what the president’s disclosure entailed, due to its sensitive nature, but said the information came from a U.S. ally. The classified information Trump shared included intelligence on ISIS that had been passed to the US by a partner, which was not identified." But Trump's disclosure was considered a potential blow to the intelligence-sharing arrangement, and White House officials reportedly moved quickly to contain the fallout"

Both Republican and Democratic lawmakers immediately voiced concern over the apparent intelligence disclosures.

“We have no way to know what was said, but protecting our nation’s secrets is paramount,” a spokesman for House Speaker Paul Ryan (R-Wis.) said in a statement. “The speaker hopes for a full explanation of the facts from the administration.”

“If it’s true, I would say it’s disturbing,” Sen. John McCain (R-Ariz.), chairman of the Senate Armed Services Committee, told CNN Monday evening.

But McCain also told The Associated Press that Trump was within his rights to share the information.