Anthony D. Weiner confirmed on Thursday that the New York City Administration for Children’s Services has opened an investigation into his treatment of his 4-year-old son, Jordan.

The inquiry comes after Mr. Weiner was embarrassed yet again this week by revelations that he had sent sexually charged messages over social media to a woman he had never met. One message showed his son in a photograph that also included Mr. Weiner’s crotch.

Though The New York Post reported on Wednesday that the child welfare agency had begun looking into the matter, citing anonymous sources, Mr. Weiner told The New York Times the same day that he had not yet been contacted.

On Thursday, however, he said that the agency had left a bare-bones letter about the investigation at his mother’s house.