Federal authorities are looking for a woman whose former romantic partner says she took a laptop from the office of the House speaker, Nancy Pelosi, during the riot at the US Capitol earlier this month.

The FBI said in an arrest warrant on Sunday, however, that Riley June Williams has not been charged with theft but only with illegally entering the Capitol and with disorderly conduct.

FBI officials said a caller claiming to be an ex of Williams said friends of hers showed him a video of her taking a laptop computer or hard drive from Pelosi’s office. The caller alleged that she intended to send the device to a friend in Russia who planned to sell it to that country’s foreign intelligence service, but that plan fell through and she either has the device or has destroyed it.

The FBI says the matter remains under investigation.

Pelosi’s deputy chief of staff, Drew Hammill, confirmed on 8 January that a laptop was taken from a conference room but said “it was a laptop that was only used for presentations”.

Williams’ mother, who lives with her in Harrisburg, Pennsylvania, told ITV reporters that her daughter had taken a sudden interest in Donald Trump’s politics and “far-right message boards”. Her father, who lives in Camp Hill, told local law enforcement officers that he and his daughter went to Washington on the day of the protest but did not stay together, meeting up later to return to Harrisburg, the FBI said.

FBI officials said they believe Williams “has fled”. Her mother told local law enforcement that she packed a bag and left, saying she would be gone for a couple of weeks. She also changed her phone number and deleted a number of social media accounts, the FBI said. Court documents do not list an attorney for her.