WALNUT CREEK (CBS SF) — Firefighters in Contra Costa County spent much of the evening on July 4 battling dozens of fires, many caused by fireworks carelessly set off by revelers in the East Bay.

As the sun set Saturday evening, the phone began ringing off the hook at the Contra Costa County Fire’s dispatch center.

Fires — many triggered by the use of illegal fireworks — were igniting across the county, threatening structures and residents and stretching firefighting resources to their very limits.

“Con Fire is currently on scene 12 grass, vegetation and structure fires across the District. In the 9 pm hour we have responded to more than 50 fires. Due to the overwhelming volume of fires we are reducing responses to all but structure fires,” the embattled agency tweeted.

As to a cause of the blazes, the agency tweeted: “Several of these are threatening structures & many caused by fireworks — beyond irresponsible in these conditions, threatening residents, firefighters & homes.”

There were at least three grass fires burning — at Lettia Rd in San Pablo; at Mims Rd in Bay Point, and at San Marcos & Rio Verde in Pittsburg. Contra Costa firefighters were also battling a a vegetation fire near Merle Ave in Martinez and a structure fire on Miner Ave in San Pablo.

“Both fires have vegetation burning very near homes. Unknown fireworks involvement. Please avid areas to allow first responders access,” the agency tweeted.

By 10 p.m, even more blazes had erupted.

“In the 10 pm hour, Con Fire has responded to 18 vegetation fires across the District, including 2 known fireworks caused. A major fire on Southwood Dr in Pittsburg is threatening multiple homes. On O St in Antioch fire brought down power lines creating hazards,” the fire department tweeted.

Contra Costa Fire said that up to 20 homes were threatened by the fire in Pittsburg that was put out by the county fire department and other local agencies.

The Contra Costa County Fire Department tweeted that crews had responded to 67 fires between 7 p.m. and midnight Saturday, with 30 fires reported during the 9 p.m hour alone. Despite the volume of calls due to fireworks on Saturday night, no homes were damaged by the fires..

Among those fire was one blaze in Antioch started by fireworks.

It marked a second straight day that Contra Costa firefighters were confronted with numerous fires.

“Yesterday we had 13 different fires — three of which we know were caused by fireworks,” explained Capt. Tracie Dutter with Contra Costa Fire. “So we had a pretty busy evening.”

The evening was busy — even with extra staff on duty in anticipation of trouble. Like much of the Bay Area this county has seen an explosion of illegal fireworks in recent weeks.

“Loud, every night,” said local resident Luis Arroyo. “It’s just been a lot of fireworks.”

With a sweeping hillside panorama from his Pittsburg home, Arroyo can see the show every year.

“Compared to over 20 years, this is the worst I’ve ever seen,” he says.

All fireworks are illegal in Contra Costa County but there is no easy way to keep them out.

“You can get it in other states,” Dutter said. “You can get it in Mexico. So it’s hard to say exactly where it’s coming from.”