CONCORD, Calif. (KRON) – Authorities are investigating after a massive fire broke out in Concord overnight.

Workers in the area say the fire was so large you could see it from miles away, lighting up the hillside.

Witnesses say they heard fireworks just before the fire started. It broke out off Evora Road, near Willow Pass and Highway 4.

That’s located in the foothills just east of Concord, with the fire spreading towards Bay Point.

Fire officials say lately they have seen an uptick in grass fires.

“We’ve been very busy since May with an almost four-fold increase in vegetation and grass fire responses, dozens of those, particularly in the last two to three weeks, have been caused by fireworks use,” said Deputy Fire Chief Lewis Broschard.

While the cause of the fire remains under investigation, officials are reminding everyone to be mindful as the 4th of July holiday weekend nears.

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