In December, NBC News reported that a Mueller report could be delivered to the attorney general as soon as mid-February.
Democratic lawmakers have demanded that Mueller's findings be made public. Top Democrats have said that any potential talk of impeachment is contingent on whether Mueller uncovers new evidence of wrongdoing.
Earlier Friday, Sen. Dianne Feinstein, D-Calif., reiterated her demands that a report be provided to Congress and the public. She said that Mueller's potential report concerned matters that had "implications for the rule of law and stability of our democracy" and that they "cannot be hidden away."
"A summary written by Attorney General Barr in place of the Mueller report will not be acceptable," Feinstein said.
In a letter to Barr dated Friday, the chairs of six influential House committees suggested that withholding evidence uncovered by Mueller could be the means for a "cover-up."
"After nearly two years of investigation — accompanied by two years of direct attacks on the integrity of the investigation by the President — the public is entitled to know what the Special Counsel has found," wrote the Democrats, including Rep. Jerry Nadler of New York, Rep. Adam Schiff of California, Rep. Elijah Cummings of Maryland, Rep. Eliot Engel of New York, Rep. Maxine Waters of California and Rep. Richard Neal of Massachusetts.