Democratic Senator Ed Markey on Monday asked for answers from Facebook Chief Executive Mark Zuckerberg after new research suggested the social media company failed to prevent display of harmful advertisements to teen Facebook users.

Markey cited comments by a Facebook executive before Congress last week that the site does not allow weight loss ads to be shown to people under the age of 18 already or any tobacco ads. Markey said "new research shows Facebook allowed advertisers to target with exactly these types of inappropriate and dangerous content to teen users." Facebook did not immediately comment.