Faegre Drinker Biddle & Reath on Tuesday closed all 22 of its offices for the day, including outposts in LA, San Francisco, and East Palo Alto, amid concerns that personnel in its Washington, D.C., office were potentially exposed to COVID-19.

None of the firm’s lawyers and staffers have tested positive for the coronavirus, but a person who attended a recent event at Faegre Drinker’s Washington office did, the firm said in a statement. As a result, the firm’s executive leadership decided Monday to close the firm’s offices.