WASHINGTON — The leaders of a congressional inquiry into Russia’s efforts to sway the U.S. election called Wednesday for the Justice Department to produce any evidence that supports President Trump’s explosive wiretapping allegation.

Declaring that Congress “must get to the bottom” of Trump’s claim, Sens. Lindsey Graham, R-S.C., and Sheldon Whitehouse, D-R.I., asked Acting Deputy Attorney General Dana Boente and FBI Director James Comey to produce the paper trail created when the Justice Department’s criminal division secures warrants for wiretaps.

Trump tweeted last weekend that former President Barack Obama had tapped his phones at Trump Tower during the election. But Trump offered no evidence to back up the accusation. Through a spokesman, Obama said neither he nor any White House official had ever ordered surveillance on any U.S. citizen. Obama’s director of national intelligence, James Clapper, said nothing matching Trump’s claims had taken place.

After Trump’s tweet, Comey privately asked the Justice Department to dispute the president’s claim because he believed the allegations to be false.

As the chairman and top Democrat on the Senate Judiciary crime and terrorism subcommittee, Graham and Whitehouse said they would take very seriously “any abuse of wiretapping authorities for political reasons.”

But, they added, “We would be equally alarmed to learn that a court found enough evidence of criminal activity or contact with a foreign power to legally authorize a wiretap of President Trump, the Trump campaign or Trump Tower.”

The senators are seeking warrant applications and court orders, which they said can be scrubbed to protect secret intelligence sources and methods.

Sen. Chuck Grassley, R-Iowa, chairman of the Judiciary Committee, told Iowa reporters in a Wednesday telephone call that he needs to be able to “sort fact from fiction” before making any decisions about Trump’s wiretapping allegation.

The House and Senate Intelligence committees, and the FBI, are investigating contacts between Trump’s campaign and Russian officials, as well as whether Moscow tried to influence the 2016 election. Trump demanded that they broaden the scope of their inquiries to include Obama’s potential abuse of executive powers.

The ranking Democrat on the Senate Intelligence Committee, Sen. Mark Warner, spent a couple hours Wednesday at CIA headquarters in Langley, Va., reviewing material for the committee’s investigation into Russia’s meddling in the election and possible contacts that Trump associates had with Russians. Other committee members, including Sens. Angus King, a Maine independent, and Marco Rubio, R-Fla., also went to the CIA to read material Wednesday.