A case involving two parents arrested Saturday on suspicion of child abuse and being under the influence of drugs in connection with the death of their infant boy has been sent back to the Kern County Sheriff's Department for further investigation, prosecutors said Thursday.

The parents -- Luis Cortez and Teresa Corrales -- were arrested after detectives were called Saturday morning to a report of an infant not breathing at apartments in the 1500 block of S. Union Avenue, deputies said. Three-month-old Adrian Cortez was unresponsive and was taken to the emergency room at Mercy Hospital, where he was pronounced dead at 9:19 a.m.

Cortez, 38, said from Lerdo Jail Wednesday that he was working Saturday and doesn't know what happened. He began crying.

Corrales, 37, and Cortez are both being held without bail and immigration holds have been placed on them, according to the sheriff's departments website. The website originally said the two were scheduled to be arraigned Wednesday, but that changed after further investigation into the case was requested.

Corrales pleaded guilty to grand theft of property in 2008, and has three petty theft convictions, according to Kern County Superior Court records

Deputies said Adrian's 4-year-old sibling, who also lived at the home, was taken into protective custody.

An autopsy was scheduled this week to determine how Adrian died.