CASTAIC, Calif. (CNS) — Firefighters were working to put out hot spots Saturday after a brush fire in Castaic which burned at least 552 acres was 97% contained by fire lines.

The North Fire was reported about 1:45 p.m. Wednesday in the area of 29330 The Old Road, east of the Golden State (5) Freeway, according to the Los Angeles County Fire Department.

The fire was essentially out Saturday and firefighters were patrolling the scene, putting out hot spots, said Dispatch Supervisor Miguel Ornelas.

The fire was initially reported to be about one acre in light to medium fuels, but quickly spread to at least 650 acres late Wednesday. It was downgraded slightly to 640 acres on Thursday morning after infrared mapping, the fire department reported.

The fire was further downgraded to 552 acres at about 7:40 p.m. Thursday due to updated mapping, according to CalFire.

Firefighters reported Wednesday that they slowed their response to the fire due to its proximity to a Los Angeles County Sheriff's Department explosives-disposal site in the area.