They claimed they spoke with friends of Williams who allegedly showed them video of her taking a laptop or hard drive from Pelosi's office.
Along with evidence that Williams illegally entered the Capitol Building that day, the complaint also notes the FBI is investigating a tip that Williams stole either a laptop or a hard drive from House Speaker Nancy Pelosi's office during the incident.
Riley June Williams, of Harrisburg, Pa., has been charged with illegally entering the U.S. Capitol and disorderly conduct in connection with the riot, which left five people dead.
The investigation notes that Williams was "was seen in footage of the January 6 insurrection in area of the Capitol near Pelosi's office", Politico reports. "W1 stated that WILLIAMS meant to send the computer device to a friend in Russia, who then planned to sell the device to SVR, Russian foreign intelligence service", the court document alleged.
Pennsylvania care worker Riley June Williams is being investigated by the FBI over alleged involvement in stealing either a laptop or a hard drive from the office of House Speaker Nancy Pelosi during the 6 January riots, according to an affidavit published by the bureau.
Pelosi's deputy chief of staff, Drew Hammill, confirmed January 8 that a laptop was taken from a conference room but said "it was a laptop that was only used for presentations". The FBI is working with William's mother, who identified her daughter in the video and said she'd "taken a sudden interest in President Trump's politics and 'far-right message boards'".
Former Trump campaign staffers were listed as official event organizers and helped secure the permit for the "Save America" rally that led to the storming of the Capitol, despite repeated denials from Trump's reelection campaign that it was involved, several news organizations discovered through a review of official paperwork, the Business Insider reported on Monday.
Others have shared footage of the same woman outside the building with a heavy package in her purse.
An ITV reporter interviewed Williams' mother at her apartment after the attack. According to an arrest warrant filed Sunday night, a tipster called into the FBI's hotline and told authorities they spotted her in videos from the siege.
Williams allegedly traveled to D.C. with her father on January 6, but separated from him during the day, the warrant states.
The complaint says that after Williams returned home, she packed a bag and told her mother she was leaving "for a couple of weeks". Williams allegedly then changed her telephone number and deleted her presumed social media pages.
Apple CEO Tim Cook defends pulling Parler from app store
Amid increasing pressure on Trump for his role in inciting the violence, Parler was banned by Amazon, Apple and Google. Apple, he added, is "always trying to do the right thing".