Authorities said two accidents involving at least nine cars on Interstate 5 in Irvine left a Chula Vista woman and a number of others, including children, injured.
The California Highway Patrol said a two-vehicle accident occurred at about 1:30 a.m. Thursday in the southbound lanes of the freeway near the Alton Parkway exit.
Officials said a 24-year-old woman from Chula Vista died in the crash, and a 6-month-old child traveling with her was taken to a hospital.
There was no immediate word on the child's condition. Police said a man involved in the crash has been arrested for driving under the influence.
Officials said a seven-vehicle crash followed the initial wreck. There was no immediate word on what caused the second accident or the number of people injured.
All lanes of the freeway were closed and were expected to be shut down for a number of hours.