SACRAMENTO, Calif.—A Santa Rosa school bus driver is behind bars after being arrested on suspicion of molesting a 13-year-old boy.

Authorities say Richard Guillen was taken into custody Thursday at the Bodega Bay Marine Lab after he drove a group of children to the lab for a field trip.

The 60-year-old Guillen was arrested by Sacramento County Sheriff's detectives, who were investigating a report filed by the boy's mother with Santa Rosa police.

In the report, the mother said her son had told her that Guillen had taken him to a motel in Sacramento and sexually molested him in February.

After Guillen was arrested, he was transported to Sacramento County Mail Jail, where he was in custody on $500,000 bail. It's not known if he had hired an attorney.

Detectives did not name the bus company that employed Guillen.