The woman, who was on board the plane Monday when it went down near Riverside Municipal Airport, suffered third-degree burns to 90% of her body, Reynolds said.
The other survivor was found near the crash scene and aided by residents who assisted firefighters with the rescue, Reynolds said. Both women are in critical condition.
Three others on the plane were killed, fire officials said. The victims include an adult male, an adult female and a teenage female, Reynolds said. No one on the plane has been identified and officials weren't sure whether they were all part of the same family. Officials had said four were killed, but later corrected the number.
The Cessna 310 crashed about a half mile northeast of the airport Monday afternoon, Federal Aviation Administration spokesman Ian Gregor said. It had departed Riverside en route to San Jose.
Four homes were damaged in the crash, Reynolds said. Two were destroyed by fire, while two others sustained minor exterior damage.
No one on the ground was hurt, fire officials said, though more than a dozen residents were displaced, according to Riverside City Council member Mike Soubirous.
Those on board the plane had been in Southern California for a cheerleading competition at Disneyland, Riverside Fire Chief Michael Moore said.
"This is supposedly a happy time and then just to have a tragic incident like this, and into one of these Riverside residences, it's really a sad case for us," Moore said.
A team from the National Transportation Safety Board, which arrived at the scene Tuesday morning, is investigating. The agency began gathering information from the site, including witness statements, said Stephen Stein, an NTSB air safety investigator.
Stein said the investigation is in the early stages. Making a determination on the cause of the crash could take more than 18 months.
Once the wreckage is recovered, he said, investigators will gather archived information related to the pilot, the plane and environmental conditions.
Investigators don't know who was flying the plane, Stein said.
The aircraft had a full tank of fuel, causing the fire to burn fiercely. Investigators also want to assess the neighborhood in case of dropped plane parts, as debris was scattered in the impact.
"The airplane itself ... it's in quite a few pieces spread over a debris field," Stein said. "It spreads about 100 feet, maybe 150 feet."
The crash happened at 4:41 p.m. Monday (7:41 p.m. ET) on Central and Streeter avenues, police Lt. Charles Payne said.
Brian Marsh told CNN affiliate KTLA
that he saw the plane fall from the sky.
"As soon as it turned, it almost stalled," Marsh said. "It just turned and went straight toward the ground. It looked like they tried to pull out of it, but it was too late."
Traci Zamora, who lives in the neighborhood, heard the crash.
"I was inside the house and it shook our whole house like an earthquake," she told CNN over Facebook. "It is all so surreal."
Another resident, Chloe Hirohata, told CNN in an email, "I heard an explosion, witnessed a large plume of smoke coming from the scene and rushed over."