The city police announced this on their Twitter page.

"Update: The suspect has been taken into custody," the statement said.

UPDATE: Suspect in custody

Officials from @CapitolPolice, with the assistance of MPD and @ATFWashington, provide an update regarding the active bomb threat situation near the Library of Congress

- DC Police Department (@DCPoliceDept) August 19, 2021

Earlier, Capitol police warned of the threat of an explosion at the US Library of Congress.