A man caught “attempting to start a fire” Thursday in a West Hills neighborhood that was already burning from the Kenneth fire is now under investigation for potentially igniting the near-1,000-acre blaze, according to law enforcement officials and a document reviewed by The Times.

Juan Sierra, 33, was arrested by officers from the Los Angeles Police Department’s Topanga Division around 5:30 p.m. after he was seen attempting to spark a fire, according to a law enforcement email obtained by The Times.

While Sierra was only arrested on suspicion of a probation violation, Ventura County Sheriff’s Department Sgt. Monica Smith said Friday that he is a “person of interest” in the Kenneth fire, which ignited Thursday afternoon near the county line and was threatening homes in Calabasas and Hidden Hills.

Fanned by strong Santa Ana winds, the fire had consumed roughly 960 acres of brush by 5:30 p.m. Thursday and was burning south through open space toward homes in the Malibu Canyon area north of the 101 Freeway near Calabasas. But a series of water drops helped slow its advance. The blaze is about 35% contained, and evacuation orders have been lifted, fire officials said.

Smith said authorities have not ruled out arson as the cause of the blaze. Officer Drake Madison, an LAPD spokesman, said Sierra was spotted attempting to start a fire in the 21700 block of Ybarra Road at 4:32 p.m. Police made the arrest after Sierra was detained by residents who claimed they saw him setting a fire, according to two law enforcement sources who spoke on the condition of anonymity to discuss an ongoing investigation. He has not been charged with setting the fire.

While Sierra was being held in LAPD custody, officials determined the origin point of the Kenneth fire was in Ventura County, so the investigation has been turned over to the Ventura County Sheriff’s Office .

A man with Sierra’s same birthday has been arrested at least three other times by Los Angeles police since 2023, according to L.A. County jail records. It was not immediately clear what his prior arrests were for, or what offense he was on probation for. A spokeswoman for the L.A. County Probation Department did not immediately respond to a request for comment.