VISTA, Calif. -- A 28-year-old San Marcos husband was in custody Friday on suspicion of having a sexual relationship with a 13-year-old girlfriend, a San Diego sheriff's sergeant said.

Eduardo Martinez Cruz was booked into the Vista Detention Facility on suspicion of a lewd act on a child, said Sgt. Karen Stubkjaer.

The investigation began Thursday morning when the 13-year-old girl was reported missing from her Vista home, Stubkjaer said.

When a deputy arrived, the girl had already returned home. While questioning the girl and her family, the deputy determined the girl had a boyfriend in his late 20s who provided her with a cell phone so they could arrange late-night rendezvous, during which they allegedly had sex, Stubkjaer said.

Around 10:50 p.m. Thursday, a San Marcos woman called deputies and said she believed her husband was the suspect in a child rape case, Stubkjaer said.

The woman said she was afraid he might flee to Mexico. Deputies arrived at the residence and arrested Cruz, she said.