NEW YORK (AP) — Facebook is having one of its worst weeks as a publicly traded company with a share sell-off continuing for a second day.

Britain's Commissioner Elizabeth Denham told the BBC that she was investigating Facebook and has asked the company not to pursue its own audit of Cambridge Analytica's data use. Denham is also pursuing a warrant to search Cambridge Analytica's servers.

Facebook's stock tumbled 2 percent at the opening bell Tuesday following its worst trading day in four years.

Facebook Inc. is coming under intense scrutiny since The New York Times and The Guardian newspaper reported that former Trump campaign consultant Cambridge Analytica used data, including user likes, inappropriately obtained from roughly 50 million Facebook users to try to sway elections.