Senate Majority Leader Chuck Schumer (D-N.Y.) on Tuesday called for the Biden administration to brief senators on the leak of a set of highly classified documents about the Ukraine war.

A Schumer spokesperson announced the request. No date or time has been set yet for the briefing. The Senate is in recess and will return next week.

The leaked documents include those warning of weaknesses in Ukraine’s defenses, ammunition shortfalls and weaknesses in air defense, The Washington Post reported over the weekend.

One of the leaked Pentagon documents said that the Ukrainian air defense may not be able to protect their front lines through the end of May. 

“[Ukraine’s] ability to provide medium range air defense to protect the [front lines] will be completely reduced by May 23,” one document from the Defense Department’s Joint Staff in February said, according to the Post.

“As 1st Layer Defense munitions run out, 2nd and 3rd Layer expenditure rates will increase, reducing the ability to defend against Russian aerial attacks from all altitudes,” the classified document says.

The Justice Department and the Pentagon are investigating the origin of the leaks.

“The Department of Defense is working around the clock to look at the scope and scale of the distribution, the assessed impact and our mitigation measures,” Chris Meagher, assistant to the secretary of Defense for public affairs, told reporters on Monday.

Defense Secretary Lloyd Austin became aware of the leaked documents on April 6, with more coming online in the following days. 

The documents cover a range of different topics, including U.S. and NATO support for Ukraine. Others discuss other nations, including South Korea and Israel. 

Ukraine on Sunday alleged that Russia altered the Pentagon’s documents 

“In recent decades, the most successful operations of the Russian special services took place in Photoshop,” Ukrainian Defense Ministry’s intelligence directorate representative Andriy Yusov said in televised remarks. “From the preliminary analysis of these materials, we see false figures on losses from both sides.”

John Kirby, the White House spokesperson for national security affairs, told reporters on Monday that some of the documents were indeed doctored, but declined to go any further. He added that President Biden was made aware of the leaked documents late last week.