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(CNN) – Some of the fires raging through California may have been set intentionally, says Jeff Carle, former assistant fire chief for San Diego.
"My believe is just based on the fact that there were so many," says Carle, who spent 20 years investigating suspicious fires.
The stunning explosion of fires this week in San Diego County – eight in all, five still burning – stirred suspicions of arson and sent thousands of people fleeing from their homes beginning Tuesday.
While the causes of the wildfires remain unclear, arson has been a primary suspicion among residents.
Escondido police Thursday night arrested 19-year-old Isaiah Silva and a 17-year-old juvenile, both of Escondido, in connection with arson-related charges stemming from brush fires along Escondido Boulevard and Kit Carson Park, authorities said.
Every fire has an origin, says Carle, and investigators will have to search the area to detrermine if arson was involved.
"There can be a possibility that some evidence is either stepped on or washed away, but we've worked over the years very diligently with the first responding companies to have them be able to recognize where a fire was likely to have started, and to try to protect that area," says Carle.
Serial arsonists tend to be Caucasian, male, between the ages of 20 and 28 years old, and disaffected from society, says the former investigator.
"Some people use the term losers or loners. We've seen people like that in my career that were repeat offenders. And the scary thing about those particular individuals is that they tend to be very, very prolific," said Carle.