Police say a resident in the neighborhood reported seeing the boys leaving the area just after the fire started.
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Detectives tracked down the 14 and 16-year-old and during questioning, "obtained statements from the juveniles who admitted to being responsible for starting the fire."
The investigation was then turned over to the San Francisco Fire Fire Marshall, and the boys were released to their families pending the outcome of the investigation.
The fire started at 11:54 a.m. Fire officials say it burned more than 10 acres as it burned thru a grove of trees adjacent to Sign Hill, carried by strong winds.
The grass fire is fully contained and all evacuations have been lifted, officials said Friday evening.
Neighbors living near the iconic sign had only moments to react.
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For Lindy Sison and his wife, they only had five minutes to evacuate and to say goodbye to 34 years of memories.
"The police said, 'this is time to get out. You only have less than five minutes before all this catches fire here," said Sison.
When they looked outside they noticed the iconic sign hill in flames. His neighbors running to their cars. Over 121 homes evacuated. Their home was the only one directly impacted.
"The fire came through the grass there and the trees but it sparked on top this right there in the window," said Sison.
Next to the hillside Paul saw the flames just 5 feet away from his house and alerted other around him, "I saw this really big fire and a lot of smoke. I was like this is it. My thinking was I don't need to panic. Just keep it under control and pack all the important stuff. I had my go-to bag."
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Many neighbors pointed to seeing two teenagers by the hill minute prior to the fire. "Whether it was accidental or purposeful the weather encouraged the fire behavior to get this big"
125 firefighters responded to this fast moving fire. They say the low humidity and the fast winds did not make it easy to contain.
South San Francisco residents are now asking for city officials to respond to a request they've made for years. "These are eucalyptus trees. They don't want to take them down but this is our fire hazard throughout our area because we are surrounded by trees everywhere. Trees on the side, trees on the back and the front," said Sison.
"I ran to the end of the street and the trees were on fire," said neighbor Cindy Ullmann.
#BREAKING 4-alarm Grassfire burning on “sign hill’ in South SF. EVACUATIONS underway for residents living on Ridgeview Ct. Structures threatened. @CAL_FIRE doing retardant drops. pic.twitter.com/ypRqnyWX8W— Cornell Barnard (@CornellBarnard) October 16, 2020
Residents living on Ridgeview Court, Mountain Road and Carnelian Road were told to evacuate.
"There was the fire just yards away, I grabbed the kids came here hoping the house wouldn't burn down," said evacuee Albert Babakhov.
WATCH: Four-alarm fire burns on Sign Hill in South San Francisco
CAL FIRE made air drops of retardant over the blaze which grew to ten acres.
The air attack was paused, when drones were spotted flying in the area, creating a hazard CAL FIRE pilots.
"The fire bumped up to the back of homes, but it was stopped and didn't reach the interior of any homes," said South San Francisco Fire Chief Jess Magallanes.
The fire was under control in about 90 minutes.
Authorities say the cause of the fire is under investigation.
Smoke from a fire in South San Francisco. Just shot this from a school in Daly City. pic.twitter.com/xRYzIVjNmd— Kate Larsen (@KateABC7) October 16, 2020