First responders "discovered a fixed wing single-engine airplane on fire atop the bluff of the San Joaquin River," the Fresno County Sheriff's Office said in a statement. "Firefighters were able to extinguish the flames and prevent them from spreading onto the properties of nearby homes," Xinhua reported.
There were four people on board the plane. Two children were pronounced deceased at the scene and two adults, listed in critical condition, were rushed to hospital, according to the statement.
The US National Transportation Safety Board is sending an investigator to the crash site.
The sheriff's office has established a safety perimeter to prevent public access to the scene and preserve evidence for investigators.