Firefighters believe illegal fireworks sparked a 2-alarm blaze in eastern Antioch Saturday afternoon which damaged one house and threatened others before crews contained the fire. The two-alarm fire was reported about 2:15 p.m. Saturday in the 1300 block of Trembath Lane, just north of East 18th Street, according to the Contra Costa County Fire Protection District. It started out as a grass fire but damaged one house and destroyed a shed and some wooden fences. But crews from Con Fire and from the East Contra Costa Fire Protection District saved six houses nearby from the fire. The fire was out by about 3 p.m. Saturday. No one was injured. Fire officials reiterated Saturday that all fireworks are illegal in Contra Costa County.