(CNN) A former director of Cambridge Analytica, who visited WikiLeaks founder Julian Assange after the 2016 US presidential election, was subpoenaed by special counsel Robert Mueller's office and cooperated, according to her lawyer.

Brittany Kaiser was a director at the controversial data company that worked for the Trump campaign and visited Assange in the Ecuadorian embassy in London where he has been living since he was granted asylum to avoid extradition in 2012.

Kaiser's lawyer Jim Walden told CNN, "The Mueller subpoena was issued long ago, and Brittany has already discharged her obligations. Whatever interest there was in Brittany seems past."

The news was first reported by The Observer newspaper in London.

The special counsel's office did not immediately respond to CNN's request for comment.

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