WASHINGTON — Democrats on the Senate Finance Committee sought to stall the confirmations of Steven Mnuchin and Tom Price, President Trump’s picks for Treasury secretary and secretary of health and human services, by refusing to attend scheduled votes on Tuesday.

As Mr. Trump’s dramatic firing of his acting attorney general threw the capital into tumult, Democrats on Tuesday also seized on the contentiousness to try to block Senator Jeff Sessions’s nomination as attorney general because they said he was too close to Mr. Trump.

In describing their tactic of boycotting the votes on nominees to Treasury and to health and human services, Senator Ron Wyden of Oregon said that recent news reports suggested Mr. Mnuchin and Mr. Price had given false statements in their nomination hearings. He said more information was needed before making judgments about the nominees.

“We have made clear that we need additional information,” Mr. Wyden said.

Senator Debbie Stabenow, Democrat of Michigan, assailed the nominees for failing to be honest with the committee.