The investigation is now focusing on who supplied the alcohol to the teenagers after a double-fatal accident this week near Arnold.
The California Highway Patrol says it´s believed an adult bought the alcohol and gave it to the boys.
Store records and surveillance camera videotapes are now being reviewed by investigators.
Officials expect their probe to take at least a few weeks, before any definitive answer is reached.
16-year-old Ernest Mann and 17-year-old Steven Ferrari were in the back seat of an Oldsmobile Tuesday night partying, when the car´s driver lost control.
The car went airborne and hit two trees before landing in a creek bed.
Mann and Ferrari were killed, and the three other teens are recovering from their injuries.