Ricky Sean Lukacs will be arraigned in adult court on Dec. 28 and is being held in juvenile hall, said Deputy District Attorney Karen Khim.

He is charged with two counts of arson of an inhabited structure for fires on Aug. 30 and 31 in the Yucaipa area, 65 miles east of Los Angeles.

Lukacs was originally arrested and charged as a juvenile, but the charges were refiled in adult court, said Susan Mickey, district attorney spokeswoman.

The fires did not cause serious injury or death, but one burned about 1 1/2 square miles in the community of Oak Glen, and the other threatened about 400 homes in Yucaipa before it was contained.