A state agent had posed as the girl, and the 51-year-old mayor was arrested Tuesday at the mall in suburban Milwaukee. District Attorney Michael Nieskes said during a news conference after a court hearing Thursday that investigators also found records of 1,800 sexually explicit chats on Becker's computer.

The charges include attempted second-degree sexual assault of a child under 16, possession of child pornography, child enticement, use of a computer to facilitate a child sex crime, attempt to expose a child to harmful material and misconduct in office. At least one city official has called on Becker to resign.

Becker, who is married and has two children, waived his preliminary hearing in Racine County Circuit Court on Thursday afternoon. Racine County Circuit Court Commissioner Alice Rudebusch set his arraignment for Feb. 10.

The investigation by the state Department of Justice's Division of Criminal Investigation started after city workers who helped Becker fix a problem with his personal computer found pornography files on it and alerted Racine police, the complaint said. Police had passed the case on to state investigators to avoid a conflict of interest.

After chatting online with the agent posing as a girl, Becker went to the mall to buy lingerie for the girl, according to a criminal complaint. During the chat, he offered to meet her and take her to a hotel to "have lots of fun," the complaint said.