The California Highway Patrol said it received 911 calls from 17 people reporting a driver was going the wrong way on two freeways before allegedly hitting another vehicle head-on, killing six.
The callers reported seeing the vehicle on the 57 and 60 freeways early Sunday morning, CHP officials said Thursday.
Officers said witnesses told them the red Camaro driven by Olivia Carolee Culbreath appeared to be going more than 100 mph.
"They were describing the vehicle, saying it was going the wrong way at a high rate of speed," CHP Officer Rodrigo Jimenez said. "But we're still asking for witnesses to call us."
Culbreath, 21, was charged Thursday with six counts of murder, according to the Los Angeles County district attorney's office. She is accused of driving the wrong direction on the 60 Freeway in Diamond Bar before smashing into a Ford Explorer.
If convicted of the murder charges, Culbreath would face a maximum sentence of life in state prison.
Jimenez declined to say where the callers were coming from or how long it was from the first 911 call to the last.
Authorities said they found evidence suggesting Culbreath was driving under the influence of alcohol at the time of the crash.
But Sarah Ardalani, a spokeswoman for the district attorney's office, said no DUI-related charges had been filed.
"The case is still under investigation," she said. "After it is completed, the complaint can be amended to include any additional charges."
Culbreath and Joel Cortez, the driver of a third vehicle caught in the crash, were the only survivors.
Four family members in the Explorer, who all died, were identified as Gregorio Mejia-Martinez, 47; Leticia Ibarra, 42; Jessica Jasmine Mejia, 20; and Ester Delgado, 80.
Culbreath's passengers -- her sister Maya, 24; and a friend, Kristin Melissa Young, 21 -- were also killed.
Culbreath remained hospitalized and in custody in lieu of $6-million bail, the district attorney's office said.
At 17, Culbreath was convicted of drunk driving in San Bernardino County, Department of Motor Vehicles officials said. State records also show she was cited for traffic violations at least two other times.
According to the 2011 data from the DMV, the most recent available, more than 38% of fatal crashes in California involved alcohol.