A 13-year-old boy was arrested on suspicion of setting off fireworks that sparked a wildfire this week in coastal southern California, forcing the evacuations of about 100 canyon homes, authorities said.

Crews with air support protected residences from the Rancho fire as flames raced through dry brush on Monday afternoon in Laguna Beach. It was held to 4 acres (1.6 hectares) with no damage to structures.

Police initially detained two juveniles who they later determined were witnesses, not suspects, the city said in a statement on Tuesday.

“Officers later obtained video evidence clearly showing a juvenile suspect lighting a firework and fleeing the scene,” the statement said.

The 13-year-old was taken into custody a short time later and could face charges including felony reckless burning of forest land, officials said. The teen was released to his parents.

The Laguna Beach blaze was one of dozens of wildfires burning this week in the state. The risk of fire was especially high on Wednesday as temperatures spiked and humidity dropped across inland southern California.

The Madre fire became California’s largest blaze so far this year, ripping through grasslands after breaking out 2 July in south-eastern San Luis Obispo county. By Wednesday, it covered more than 125 sq miles (323 sq km). It was more than 60% contained.