CHULA VISTA (CNS) - The death of a newborn baby whose body was found in his teenage mother's bed at her family's South Bay home was under investigation Wednesday.

The 17-year-old girl's parents made a 911 call about 8:30 p.m. Monday to report finding the lifeless infant at their residence in the 4000 block of Main Street in Chula Vista, according to police.

Investigators determined that the baby likely had been born 24 to 36 hours earlier, Lt. Fritz Reber said. The infant's mother told them she had been unaware that she was pregnant and had given birth unknowingly.

The baby appeared to have been born following a full-term pregnancy, weighed about 7 1/2 pounds and showed no signs of suspicious injuries, the lieutenant said.

Detectives have been interviewing witnesses and working with the county Medical Examiner's Office to determine if any crimes were committed in the case, according to police.

An autopsy was conducted Tuesday, but a ruling on the baby's cause and manner of death remained on hold pending further investigation, Reber said.