A 16-year-old girl suffered potentially life-threatening injuries when she was struck by a vehicle near a busy intersection just west of San Marcos High School early Thursday morning, authorities said. The collision happened just after 6:30 a.m. on South Rancho Santa Fe Road just south of San Marcos Boulevard, the Sheriff’s Department said. People called 911 and told dispatchers that a teenager had been struck and remained down in the roadway, the department said in a news release. The San Marcos firefighters immediately render medical aid to the girl, then took her to a hospital with “major, potentially life-threatening injuries,” the department said. The initial investigation indicates the driver was headed north on South Rancho Santa Fe Road, headed toward the intersection with San Marcos Boulevard when the teen crossed the road. The driver stayed at the crash scene and is cooperating with investigators. Neither drugs nor alcohol are believed to have been a factor in the collision, authorities said. Authorities did not say whether the teen was a student at the high school. Investigators are asking anyone who witnessed collision or caught it on dash cam to contact Sheriff’s Deputy James Clone at 760-510-5047 or via email at [email protected].