Five others inside the vehicle were killed when the four door Nissan slammed into a concrete pillar around 4:13 a.m. Saturday, according to Burbank police.
The incident happened on North San Fernando Boulevard near an off-ramp of the 5 Freeway.
The car burst into flames and was fully engulfed when officers arrived.
“This was a tough one. I’ve been here 28 years and the five fatalities is pretty rough,” Burbank Police Sgt. Darin Ryburn said during a news conference.
Speed was a factor in the wreck, Sgt. Ryburn added.
The five people who died were identified as Sugey Cuevas, Malak Hariri, Sameer Nevarez, Stephen Stoll and Sebastian Forero, family and friends told KTLA 5.
Their ages were unclear.
Police were awaiting the results of toxicology tests to determine if alcohol or drugs contributed to the crash.
Officials initially said Underwood was ejected from the car, but later retracted the statement to say she crawled out of the wreckage.
Family and friends of the victims held an emotional vigil near the crash scene on Saturday evening.
Several people at the vigil told KTLA 5 the victims had just left a party.