FILE PHOTO: A surveillance image released by the FBI shows a person in Washington, U.S., January 6, 2021. The FBI issued a notice, which features this surveillance photo, requesting information on person(s) responsible for pipe bombs left at the Republican National Committee (RNC) and Democratic National Committee (DNC) headquarters. FBI/Handout via REUTERS/File Photo

By Andrew Goudsward and Sarah N. Lynch

WASHINGTON, Dec 5 (Reuters) - The man suspected of planting pipe bombs in Washington the night before the January 6, 2021, U.S. Capitol attack appeared in court on Friday to face federal criminal charges, a day after his arrest in a case that long vexed investigators.

Brian Cole Jr., 30, of Virginia, appeared in Washington federal court with his attorney to face two explosives-related charges.

Wearing a tan prison jumpsuit, Cole calmly answered "yes" to a series of questions from a federal magistrate judge about whether he understood his rights.

Cole has been cooperating with the FBI since his arrest and has told agents he believes conspiracy theories spread by President Donald Trump about the 2020 election, according to two sources briefed on the investigation. Trump continues to falsely claim that his defeat by Democrat Joe Biden was the result of widespread fraud, a view that inspired the attack on the Capitol by his supporters.

Investigators are also exploring indications that Cole may hold anarchist views, one of the sources added.

DETENTION HEARING SET

Prosecutors indicated they will seek to keep Cole in custody to await a trial. U.S. Magistrate Judge Moxila Upadhyaya set a December 15 hearing on that request.

Cole has not yet entered a plea to the charges.

Cole was accused of placing pipe bombs outside the headquarters of the Democratic and Republican parties near the U.S. Capitol on the evening of January 5, 2021.

The devices were not discovered until the next day and were deactivated by police. Neither exploded.

Still, FBI officials have said the bombs required significant police resources just as thousands of Trump supporters surged into the U.S. Capitol in a failed bid to stop Congress from certifying the results of the 2020 election.

UNCLEAR IF INCIDENT LINKED TO RIOT

Justice Department officials have not said if there was any link between the placement of the bombs and the Capitol riot.

Investigators traced purchases of several components used in the bombs, including pipes, kitchen timers and battery connectors to Cole, according to an FBI affidavit laying out the evidence in the case.

Cell phone and license plate data also placed him in Washington near the Democratic National Committee and Republican National Committee buildings that evening, according to the affidavit.

The charges carry a potential sentence of up to 20 years in prison.

Attorney General Pam Bondi said on Thursday that there was no new information that led authorities to Cole, but that a review of existing evidence led to the identification of the suspect.

Trump-nominated FBI leaders Kash Patel and Dan Bongino placed a renewed emphasis on solving the case, which remained open for years and became fodder for right-wing conspiracy theories about the Capitol riot.

(Reporting by Andrew Goudsward and Sarah N. Lynch; Editing by Scott Malone, Cynthia Osterman, Chizu Nomiyama and Andrea Ricci )