LOS ANGELES—A curfew officially took effect overnight barring anyone without authorization from entering areas under mandatory evacuation orders due to the Palisades and Eaton fires, and county Sheriff Robert Luna warned that it will be “strictly enforced.”

The curfew will be in effect nightly from 6 p.m. to 6 a.m. the following morning. Anyone arrested for a curfew violation could face a misdemeanor charge carrying a fine of up to $1,000 and possible jail time, Luna said.

The move comes following news that 20 people had been arrested for allegedly looting in the fire zones, an act Luna on Thursday called “absolutely unacceptable.”

“You cannot be in these affected areas,” Luna said during a Friday morning briefing. “If you are, you are subject to arrest. That is important. We’re not doing this to inconvenience anybody. we’re doing this to protect the structures, houses people have left because we ordered them to leave.”

Luna said only “disaster workers” would be permitted into the affected areas. He said properly credentialed media will also be admitted into the area.

The sheriff also insisted that nobody arrested for an alleged curfew violation will be cited and released.

“They’re going to get booked,” Luna said. “We’re not screwing around with this.”

Luna said roughly 500 sheriff’s department personnel have been deployed in the fire areas and were patrolling for looters, as well as engaging in traffic control and other enforcement duties.

Members of the California National Guard were also deployed overnight to the Eaton Fire area, and additional Guard members are expected to arrive in the next 12 to 24 hours, Luna said. Some of those members are expected to be deployed to the Palisades Fire area, and the sheriff said some could also be deployed to cities such as Santa Monica, Pasadena, Azusa and Arcadia, all of which have requested assistance from the Guard.

According to the governor’s office, the Guard members “will be stationed at traffic control points to ensure the safety of the surrounding community. In addition, their support helps build capacity of local law enforcement to support their respective areas.”

District Attorney Nathan Hochman insisted that people arrested for curfew violations or any other criminal activity relating to the fires will be prosecuted.

“If you want to ... loot, if you want to commit burglary, if you want to commit grand theft ... you will be arrested, you will be prosecuted and you will be punished to the full extent of the law,” Hochman said Thursday. “These acts are despicable.”