The FBI and the New York Police Department have opened preliminary investigations of allegations that the former New York Democratic congressman exchanged sexually explicit text messages with a purportedly underage girl.
Spokespersons for the US Attorney's Office in Manhattan and the FBI declined to comment.
The allegations first surfaced in the Daily Mail
The online sexting relationship allegedly went on for months between Weiner and a girl claiming to be just 15. The Daily Mail reported she said he sent her numerous photos, one of him in a pool and at least one bare-chested.
The outlet reported that the girl said she reached out to Weiner in January on Twitter.
In a statement to CNN, Weiner neither confirmed or denied sending the texts.
"I have repeatedly demonstrated terrible judgment about the people I have communicated with online and the things I have sent. I am filled with regret and heartbroken for those I have hurt," he said.
Weiner continued: "While I have provided the Daily Mail with information showing that I have likely been the subject of a hoax, I have no one to blame but me for putting myself in this position. I am sorry."
CNN has not been able to confirm this was a hoax.
In a statement, a spokeswoman for Republican presidential nominee Donald Trump noted that Weiner donated $550 to Hillary Clinton's presidential campaign last year.
"The announcement by the FBI and New York Police Department that they are investigating close Clinton ally Anthony Weiner's inappropriate relationship with an underaged female is extremely disturbing," Jessica Ditto said. "The Clinton campaign should immediately return all campaign contributions from Weiner. America has had enough of the sleaze that is Clinton, Inc."
Huma Abedin, one of Clinton's closest aides, announced last month that she was separating from Weiner after photos emerged of him allegedly sexting with another woman while their son was in bed with him.
That woman was described
in the New York Post as a 40-something divorced woman from the West.
Weiner left Congress in June 2011 when sexually-charged, sometimes explicit, texts with women other than his wife first emerged. His social media habits continued after leaving Congress and contributed to his poor showing in the 2013 New York City mayoral race, a contest in which he had once been a leading contender.