MADISON, Wis. -

A registered sex offender talked to a girl he didn't know last week on Madison's east side and followed her two days later, police said.

Madison police said a 13-year-old was on Powers Avenue Tuesday at about 3:30 p.m. when she said a stranger waved her over to the window of his van and asked her how old she was. The girl became uncomfortable, walked away, and reported the contact to a parent.

Police said the same girl saw the van again on Thursday at about 5 p.m. while she was walking home and believed she was being followed. She was able to get a license plate number.

Using the plate number, police were able to locate the van and later its driver. The driver told police he recently moved into the neighborhood and acknowledged contacting a girl while seeking directions.

The man, who is in his 50s, is a registered sex offender but is no longer on supervision, and officers did not have probable cause to arrest him for a crime, according to the report.

Police said the department shared information on the case with all MPD officers and with the Madison Metropolitan School District.

Police also said children are encouraged to avoid contact with motorists they don't know, and immediately report, like the girl in this case did, any suspicious encounters to trusted adults so police can be notified.

Police said the van the man was driving is white.