Firefighters from the Orange County Fire Authority and the Laguna Beach Fire Department placed the Rancho Fire under unified command on Monday after the brush blaze ignited shortly after 2:15 p.m. near Rancho Laguna Road and Morningside Drive. The fire was mapped at three to four acres in steep, brush-covered terrain and was advancing toward hillside homes. Mandatory evacuation orders were issued for residents on La Mirada Street, Katella Street, Summit Drive and Baja Street, while an evacuation warning covered the Arch Beach Heights neighborhood. The city opened a temporary shelter at the Community and Susi Q Center at 380 Third Street, and authorities urged drivers to avoid the Coast Highway, where traffic quickly backed up as engines and patrol cars moved into the area. Ground crews were backed by a heavy air assault that included Air Attack 330, four fixed-wing tankers and at least six helicopters from Orange, Los Angeles and Ventura counties. By late afternoon, tankers were released as helicopter water drops and structure-protection lines helped keep flames from homes, though officials warned that spot fires were occurring outside containment lines. No injuries were reported, and the cause of the blaze remained under investigation amid unconfirmed reports that fireworks may have sparked the fire.