RAINBOW VALLEY, Ariz. -- An 18-year-old illegal immigrant has been arrested in connection with the rape of an 11-year-old girl, Maricopa County sheriff's deputies said.

Enrique Jacobo-Valdez was booked into the Fourth Avenue Jail on two counts of sexual conduct with a minor.

Jacobo-Valdez is currently unemployed and had a warrant out for his arrest from Pinal County for possession of dangerous drugs, deputies said.

He was living with the child's family at the time of the alleged incident. He was a family friend they took in four years ago.

"You think you think you're taking care of kids the right way, then something unexpected happens," the victim's grandmother said. "Just recently, I think, we started picking up on little things like they wanted to be together."

The sheriff's office said it dispatched deputies after receiving a phone call Thursday from the victim's grandmother indicating that she found the 11-year-old locked inside a bedroom.

The man was running from the home when the girl finally opened the door, sheriff's investigators said.

The grandmother and mother of the victim took the girl to a local hospital where it was determined that she is at least six weeks pregnant and may have been infected with a sexually transmitted disease during the rape, deputies said.

Jacobo-Valdez returned to the girls' home where he was arrested by deputies for the Pinal County felony warrant, according to MCSO.

"If the criminal justice system in Pinal County had done what we do, the suspect might have been deported or held in jail and that little girl would have be spared this fate," said Maricopa County Sheriff Joe Arpaio.

During an interrogation, he admitted raping the 11-year-old, sheriff's deputies said.