Nearly four months after the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives began investigating the Palisades fire, investigators set a fire to parts of the Temescal Ridge Trail between Skull Rock and Green Peak on Tuesday night into Wednesday morning.

Fire may be visible between Skull Rock and Green Peak, close to what is believed to be ground zero of the massive and deadly Palisades Fire.

ATF investigators said they are testing flame size and location, which is helpful in determining the fire’s origins.