BERKELEY -- University of California police arrested a 50-year-old sex offender early Wednesday on suspicion of sexual battery in connection with an sexual assault on a woman Monday night near People's Park.

Police arrested Roger Lopez at 1:50 a.m. Wednesday at the intersection of Bancroft and Ellsworth. Lopez had an outstanding warrant for aggravated assault and he is a sex offender who is not registered, which is required under state law, police said.

UC Berkeley police said a 25-year woman was walking east in the 2600 block of Dwight Way at about 9:35 p.m. Monday when a man yelled at her, ran across the street and grabbed her in the groin area. The man then ran west on Dwight Way toward People's Park, police said.

Based on the victim's description of the suspect, UC Berkeley police detained Lopez, but he was not arrested because the victim couldn't positively identify him as her assailant. Police later developed information that he was responsible for the crime.

Anyone who witnessed the incident or who has information about the case is asked to call police at 510-642-0472 or 510-642-6760.

Follow Kristin J. Bender at Twitter.com/kjbender.