MAGNA — A convicted child sex offender, who is on the Utah Sex Offender Registry, was arrested Thursday after police say he was living with and having sexual relations with a 15-year-old girl.

An anonymous tip led investigators to a house in Magna where the man, 25, and teen girl were living in the basement of a house belonging to the girl's 20-year-old aunt, said Salt Lake County Sheriff's Lt. Don Hutson.

The relationship was consensual, although illegal under Utah law, and the aunt was apparently aware the two were living together, he said. The girl told investigators she was unaware the man was on the sex offender registry.

Roland Earl Larsen was arrested and booked into jail for investigation of 10 counts of unlawful sexual activity with a minor and four counts of failing to properly register with the registry. Hutson said those counts could have been for moving around without notifying the state of his change of addresses.

In 2003, Larsen was convicted of sexual abuse of a child, a second degree felony. Larsen received a suspended 1-to-15 year prison sentence for his conviction and given credit for his 270 days spent in jail after his arrest.

— Pat Reavy