The man who stormed Pelosi’s office and a West Virginia lawmaker are among those arrested.

A lawmaker from West Virginia and a man who broke into Speaker Nancy Pelosi’s office and posed at her desk were among those arrested on charges related to the siege at the Capitol, federal law enforcement officials announced on Friday as they promised an exhaustive investigation into the violence.

The authorities also found 11 Molotov cocktails and a semiautomatic rifle in the truck of a 70-year-old man from Alabama who was also arrested, according to prosecutors. He also had two handguns.

Hundreds of prosecutors and F.B.I. agents have been assigned to work the investigation and were pursuing dozens of cases, Ken Kohl, a prosecutor in the U.S. attorney’s office in Washington, said in a briefing with reporters.

“We are far from done,” added Steven M. D’Antuono, who runs the F.B.I.’s Washington field office.

Federal law enforcement officials have charged at least 13 people, the Justice Department said in a news release later Friday, several on charges of unlawful entry. Washington police have also arrested dozens, mostly on charges of unlawful entry and curfew violations. The United States Capitol Police announced the arrests of 14 other people on Thursday.

Among those charged was Derrick Evans, a newly elected lawmaker from West Virginia, Mr. Kohl said. Mr. Evans posted video to his Facebook page of him filming as he stood among the crowd outside a Capitol door and then rushing inside with them.

Another man, Richard Barnett, 60, from Gravette, Ark., was taken into custody and faces three counts. He had posted a picture on social media that showed him sitting at Ms. Pelosi’s desk with his feet up and said he had expected to be arrested.

“I’ll probably be telling them this is what happened all the way to the D.C. jail,” Mr. Barnett told a New York Times reporter later that day.

A day earlier, federal prosecutors filed a criminal complaint accusing a man named Mark J. Leffingwell of punching a Capitol Police officer repeatedly in the head and chest, before apologizing. Prosecutors also unsealed charges against a Maryland resident, Christopher Alberts, accusing him of illegally carrying a 9-millimeter pistol at the riot. Mr. Alberts told the police that he had the weapon for “personal protection” and did not intend to harm anyone.