The collision occurred Thursday afternoon about 3 miles southeast of town, near the Corona Municipal Airport.
CBS News correspondent Manuel Gallegus reports that the planes may have been circling the airport, waiting for a construction crew to clear the runway.
The bodies of two men were found at a condo complex, while a third body was found a half-mile away at a two-story home. The victims were not identified. "They are presumed to be the pilots and one passenger," reports Gallegus.
"There was a giant fireball in the air, and it just kept growing bigger," said George Panagotacos, who was flying his plane home to Corona and saw the collision in front of him. "It looked like the napalm in Vietnam."
The FAA said one plane was a twin-engine and the other a single-engine. It was not clear how many people were aboard or their destinations and origins.
The falling debris triggered fires that dozens of firefighters needed two hours to extinguish.
"All of a sudden, the window shatters and fire rolls in," said condo resident Scott Gurganious, 24. He, his 2-year-old son, his wife and a child they were caring for escaped the blaze uninjured.
About 20 families at the complex were left homeless, said building manager Naomi Marples. Four units were destroyed and about 12 others were damaged by debris.
Shahnaz Gauhar at first thought there was an earthquake when she heard the debris pelting her house. She made it out safely, and even as the remains of their house smoldered, she and her husband counted their blessings.
"We are extremely lucky that my wife is safe," Mohammad Gauhar said. "The house can always be repaired. It's a one in a million chance this could happen, and it happened to us."
Corona is in Riverside County, about 50 miles east of Los Angeles.
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