Investigators have identified five girls who say they are victims and they believe there could be more.
Steven Arthur and his ex-girlfriend Jennifer Thurman are being held without bail after being charged with child molestation, possessing child pornography and rape.
After receiving a tip, Porterville police were called to this house on Sandra Lane where they found thousands of images and videos of child pornography.
Sgt. Mike Blain: "There are probably in the area of 50-60 DVDs that were seized. There was a computer that was seized and there was a digital camera that was seized."
Police believe several of the girls who were molested by Arthur and Thurman live in the neighborhood.
This swingset in the backyard is empty now but neighbors say they saw children playing here all the time.
Bob Etheridge, Neighbor: "They were always over there and they would have friends, neighborhood kids always down here."
Bob Etheridge says Steven Arthur worked as an Emergency Medical Technician for a local ambulance service and seemed like a nice guy.
He's shocked by the charges against his neighbor.
Etheridge: "I think that's sick if that's really what's happening"
Sgt. Blain says he's never seen a child pornography and molestation case of this magnitude in Porterville. Detectives are still looking through all the evidence on Steven Arthur's computer.
Investigators believe the crimes took place at Arthur's house and the sexual assaults had been going on since at least September.
Sgt. Blain: "In addition to those victims we've been able to identify, there may be other victims out there and so we're asking that the public contact Porterville Police Department if they've had any contact with Steven Arthur or Jennifer Thurman."
Police say there were children living at the house.
Right now the County's Sexual Assault Team and Homeland Security are reviewing all the evidence.
