A classified ad that offered a free baby boy on the Craigslist Web site was under investigation by police Friday although the posting was believed to be a hoax.

The ad was posted to the "free stuff" section of the site early Thursday alongside offers for free turkey dinners, a set of crutches and an electric stove.

The writer, who said he was in San Diego, claimed that his ex-girlfriend had the baby a few weeks ago.

"Now he just sits in my closet and cries," the ad stated. "I'm not too sure how to deal with it."

The posting added: "Batteries not included. Transaction final. No returns."

Craigslist removed the ad shortly after it appeared.

"This is most probably a hoax," site founder Craig Newmark said in an e-mail to The Associated Press on Friday.

San Diego police said the matter was referred to investigators in the child abuse unit and another department that investigates Internet crimes against children.

"We're taking it seriously because we don't know," said police spokeswoman Monica Munoz. "Until we determine whether or not it's a hoax or not we won't let it go."