LOS ANGELES — A fast-moving brush fire raced across hundreds of acres of thick vegetation near Castaic Lake Wednesday, forcing mandatory evacuations in the lake area, Castaic and parts of Ventura County.

Los Angeles County Sheriff Robert Luna said the sheriff's Pitchess Detention Center jail facility in Castaic was under an evacuation order, and about 476 inmates were being moved from one of the complex's buildings to a different facility.

Luna said that in consultation with the fire department, a decision was made to have the roughly 4,600 inmates at the complex shelter in place inside the concrete structures, but "we do have a plan in place to evacuate the rest of the inmates ... if we absolutely had to."

After the was reported Wednesday, the ACLU of Southern California has alerted the LA County Board of Supervisors to the thousands of people in its custody at four north county jails in the Hughes Fire evacuation warning zone and demanded their immediate evacuation.

In a statement, ACLU of SoCal said:

"At least 4,700 people are incarcerated in four north county jails within the Hughes Fire evacuation warning zone. We have long opposed the expansion of the jail system especially in dangerous fire zones and we are gravely concerned for the safety of people incarcerated in those jails. We urge our county supervisors to direct the L.A. Sheriff's Department to immediately organize the transportation needed to evacuate the jails without delay.”

Luna said roughly 31,000 people are under evacuation orders due to the fire, and 25,000 more are under evacuation warnings.

The Hughes Fire is more than 9,400 acres, according to county Fire Chief Anthony Marrone, with 0% containment, and so far, no structures burned.