Investigators were trying to learn whether any adults attended a party at Yosemite Lake and whether they let a 15-year-old girl drive off in a car that crashed into another vehicle, killing two other youths. The girl suffered cuts and bruises. California Highway Patrol officers were told that the girl had been drinking "spiked punch" and drove off in the car on a dare. "If she was out there with adults, we want to see if someone else was more culpable than this teen-ager," CHP spokesman Tom Sawyer said. One victim, Samuel Conti, 18, had graduated from Merced High School Thursday. The crash also killed his girlfriend, 15-year-old Kristina Nicholas, a student at Merced High.