Key senators said Friday they supported a delay on a floor vote on Supreme Court nominee Brett Kavanaugh to allow for an FBI investigation of sexual assault allegations against the judge, as a Senate panel voted to advance the nomination.

Republican Sens. Jeff Flake of Arizona, Lisa Murkowski of Alaska and Susan Collins of Maine, as well as West Virginia Democrat Joe Manchin and North Dakota Democrat Heidi Heitkamp, said that they supported delaying a floor vote in order to allow the FBI to conduct a weeklong investigation. The Senate Judiciary Committee later said it would request that the FBI carry out a "supplemental" background check of Kavanaugh that will take no more than a week from Friday.

The idea was first broached by Flake, who announced the plan during a dramatic standoff ahead of the Judiciary Commitee's 11-10 party line vote on Kavanaugh's nomination Friday afternoon.

"I think that we ought to do what we can to make sure that we do all due diligence with a nomination this important," Flake said. Flake said he supported an investigation that was "limited in time and scope to the current allegations that are there."

The Senate is narrowly divided, with Republicans holding a slim 51-49 majority. The party needs only 50 votes to secure Kavanaugh's confirmation. That means all eyes will be on four key senators, two Republicans and two Democrats, including Murkowski and Manchin, who have not yet said how they will vote.

Flake's remarks Friday immediately sparked confusion among the lawmakers. As of Friday afternoon, it was unclear what mechanism would be used to bring the FBI into the Kavanaugh probe. Traditionally, the White House, and not the Senate, would be required to instruct the FBI to conduct an investigation.

A cloud of uncertainty loomed large in the committee chamber Friday. As the committee's Republican Chairman Chuck Grassley, R-Iowa, called for a vote in the seconds following Flake's announcement, the top Democrat on the panel, Sen. Dianne Feinstein of California, asked what exactly the committee was voting on.