CONCORD (CBS SF) — Contra Costa County fire crews were busy Sunday night responding to a flurry of 911 calls reporting several blazes including a home fires in Pittsburg and Antioch, a hillside brushfire threatening homes in Martinez and two small blazes ignited during a July 4th fireworks show at the Concord Pavilion.

Con Fire responded to 48 grass-exterior fires and 5 structure fires across the county Sunday night and early Monday, a major reductions in the calls from last Independence Day evening.

Officials have been warning local residents for weeks about the fire danger posed by the combination of illegal fireworks use and the tinder-dry hills from the extreme drought conditions.

But as night fell Sunday, the sounds of exploding fireworks echoed across the county.

A fire erupted on a hillside in unincorporated Martinez on the 500 block of Ross Circle. The flames were visible from 680 and threatened nearby homes until firefighters were able to gain control.

At 10:15 p.m., Contra Costa fire officials posted on social media that firefighters were “currently on-scene 7 separate grass & exterior fires across the district as well as a residential fire caused by fireworks on roof at 18th & Viera in Antioch.”

A blaze early Sunday evening charred the exterior of a single family home on Deems St. in Pittsburg. Officials said the blaze was caused by fireworks shot into the backyard.

The July 4th fireworks show at the Concord Pavilion was halted twice as a nearby hillside caught fire. It was not immediately known if sparks from the show ignited the two small fires or if they came from illegal fireworks use were to blame.

The fires were quickly extinguished by fire crews posted at the show as a precaution.

Meanwhile in North Richmond, fire crews were slowed by a large crowd in their efforts to respond to a fire.

“There’s a vegetation fire in North Richmond and 200 people have assembled preventing access to the fire,” tweeted Contra Costa County Supervisor John Gioia.