The House Ethics Committee has begun a preliminary inquiry into Rep. Anthony Weiner (D-N.Y.), the Associated Press reported Monday, citing House officials.

A preliminary inquiry is the first step in any formal Ethics Committee investigation. Inquiries are undertaken to determine whether the matter is serious enough to warrant the formation of an investigative subcommittee, which would then have the ability to formally discipline Weiner. Even if the inquiry does not progress to that stage, committee leaders could issue an informal report admonishing Weiner for his behavior, which could be politically damaging.

House Minority Leader Nancy Pelosi (D-Calif.) called for an ethics investigation on June 6, after Weiner admitted during a news conference to communicating and exchanging sexually explicit pictures with at least six women other than his wife.

Pelosi, Democratic Congressional Campaign Committee Chairman Steve Israel (N.Y.) and Democratic National Committee Chairwoman Debbie Wasserman Schultz (Fla.) then called on Weiner to step down Saturday afternoon.

Weiner has entered treatment and asked for a leave of absence from the House. A statement Saturday from Weiner spokeswoman Risa Heller made no mention of resignation. She said he “takes the views of his colleagues very seriously and has determined that he needs this time to get healthy and make the best decision” for everyone.

Ethics experts indicated last week that Weiner and his staff could face a prolonged and expensive investigation.

Amanda Becker, Steve Peoples and John Stanton contributed to this report.