Democrats leading six House committees demanded the Justice Department release special counsel Robert Mueller’s full report to Congress by April 2, citing outstanding questions they claim were not answered in Attorney General Bill Barr’s summary of the Russia investigation provided to lawmakers Sunday.

“Your four-page summary of the Special Counsel’s review is not sufficient for Congress, as a coequal branch of government, to perform [its] critical work,” the lawmakers, including House Judiciary Chairman Jerry Nadler of New York and House Intelligence Committee Chairman Adam Schiff of California, wrote in a letter to Barr. “The release of the full report and the underlying evidence and documents is urgently needed by our committees to perform their duties under the Constitution.”

Barr’s summary came in the form of a four-page letter which stated the investigation “did not find that the Trump campaign or anyone associated with it conspired or coordinated with Russia in its efforts to influence the 2016 U.S. presidential election."

Mueller did not determine whether Trump obstructed justice, which prompted Barr and Deputy Attorney General Rod Rosenstein to decide that the evidence “is not sufficient to establish that the president committed an obstruction-of-justice offense."

The lawmakers argued they “must be permitted to make an independent assessment of the evidence regarding obstruction of justice.”

“The determinations you have reached regarding obstruction and the manner in which you chose to characterize the Special Counsel’s investigation only raise further questions, particularly in light of the Special Counsel’s decision to refrain from making “a traditional prosecutorial judgment,” the lawmakers wrote.

[Opinion: Mueller in full]

Although the lawmakers said they had no reason to doubt Mueller’s judgment, they said it is critical for Congress to examine all of the “facts and evidence” collected by Mueller for national security purposes and requested the Justice Department share the report no later than April 2.

Subpoenas were not mentioned in the Democrats' letter, but subpoena power is within their arsenal should the Justice Department fail to meet their demand by next week's deadline.

In addition to Nadler and Schiff, the letter was signed by House Oversight Committee Chairman Elijah Cummings of Maryland, House Financial Services Committee Chairwoman Maxine Waters of California, House Ways and Means Committee Chairman Richard Neal of Massachusetts, and House Foreign Affairs Committee Chairman Eliot Engel of New York.