Law enforcement agencies across Northern California investigated emailed bomb threats Thursday that were part of a nationwide hoax.The email asks businesses to pay by Bitcoin on threat of detonating a bomb. Businesses across the U.S. received similar emails, which were sent around 11 a.m. "We are aware of recent bomb threats made in cities around the country & remain in touch w/ our law enforcement partners to provide assistance. As always, we encourage the public to remain vigilant & to report suspicious activities that could represent a threat to public safety," the FBI said in a statement.The areas that reported bomb threats in NorCal are:Sacramento CountyWest SacramentoFolsomEl Dorado CountyGrass ValleyNevada CountyStocktonVacavillePlacerville RocklinLodiThe Sacramento Police Explosive Ordinance Disposal Unit said it works with several other law enforcement agencies in the region and began monitoring the threats early Thursday morning."We're on the phone constantly all day, together, and that's how it was (Thursday)," Sgt. Clayon Buchanan said."We were all talking to each other so we all knew when they were coming."Although deemed not credible, Buchanan said they pay close attention to every threat."If they're specific to an area, to a certain time, that's the stuff that we take a little bit more serious," he said.Buchanan said anytime you see or get something suspicious, call law enforcement."We want to come out and respond and keep people safe," he said.No other details were released.