Police did not provide details on how Mr Halstenberg is alleged to have sparked the massive blaze, which is burning in San Bernardino County, about 60 miles (96km) east of Los Angeles.
Thousands of people have been forced to evacuate the area and the fire threatens over 65,000 structures.
CalFire officials say the blaze continues to grow in steep terrain, making access difficult, especially near the Big Bear area.
The fire has been fuelled by strong winds and dry conditions, though firefighters hope cooler weather forecast for later in the week will help their efforts.
The structures under threat, both homes and commercial properties, include some 13,300 in areas currently under evacuation orders.
One evacuee, Blaine Bacher, said the first thing he grabbed from his home in Arrowbear Lake is his mother's ashes.
Mr Bacher told the BBC on Wednesday that he has no idea if his home is still standing.
“This home is more than just walls and a roof,” he said.
"My mother passed away in that house. I held her hand for her last breath in that house. She and my stepfather built and raised me and my sister in that house. It’s beyond priceless."
No fatalities or structural damage have been reported as a result of the Line Fire to date. However, photos taken by the Los Angeles Times appear to show at least one building in Running Springs, a community in the San Bernardino Mountains, has been destroyed.
nanoH2O on September 11st, 2024 at 16:02 UTC »
How do you even find suspects for something like this? Because they bragged to someone? Just seems so easy to throw a match or something into the brush and drive off with none the wiser.
funkiestj on September 11st, 2024 at 15:48 UTC »
The Park Fire this year up near Chico was arson too
Big-Heron4763 on September 11st, 2024 at 15:24 UTC »
What goes on in someone's mind to deliberately start a fire like this?