Meteorologist Craig Shoemaker said the loud bang heard across a wide area of the Sierra Nevada mountains originated with the Lyrid meteor shower, an annual phenomenon caused by debris from Comet Thatcher, which passes Earth every year.
The event occurred at 8:30 a.m. PDT and sparked calls to police agencies in at least three counties, the Sacramento Bee said.
"It went on for a while," Georgann Wilmont, who lives in the mountains near Sutter Creek, told the Bee. "We heard one big one and then there other rumblings. At first I thought maybe it was an earthquake."