The explosion happened around 3:45 p.m. at a home in the 4200 block of Sierra Vista Drive.
AIR7 video from above the scene shows pieces of the home scattered all over Sierra Vista Drive, and a gas line built into a wall outside the home, which burned for hours.
In a later update, the Chino Valley Fire District said the gas leak at the property was stopped at 10:45 p.m.
Now, investigators are working to figure out why the home burst into flames.
Video shows the front of the home reduced to rubble. Debris even landed in some neighbors' driveways across the street.
Neighbors said the blast felt like an earthquake.
"It shook the whole house," one neighbor said.
The neighbor and her sister didn't want to be identified, but told Eyewitness News that they saw the victims, some of them children, running from the badly burned home.
"They were just screaming for help, saying, 'Ow. It hurts! Help me!' You know, barefooted in their pajamas. The little boy without a shirt, just in his sweatpants. It was hard," one witness said.
"Their hair was burnt, they had blood on their faces," the other witness said.
The explosion was so destructive, it damaged several nearby homes.
Investigators say eight to nine victims were inside during the explosion. EMS rushed half of them to the hospital, and witnesses say a neighbor took some of the young burn victims to the hospital by car.
They are all in unknown conditions, but the San Bernardino County Sheriff's Department said it appeared none were life-threatening.
"I tried to help her. I didn't want to pick her up, because she was burnt. I didn't want to hurt her even more," a witness said.
Eyewitness News cameras captured power crews digging around the property to determine what exactly happened.
Firefighters said a total of 16 homes from Sierra Vista Drive to Del Norte Avenue were temporarily evacuated out of precaution to make sure the area was safe from further explosions. They were allowed to return at 11 p.m.
"I just hope the kids are OK. Everything else doesn't matter," one of the neighbors said.