(CNN) -- After thousands of customers in Pierce County, Washington, were affected Sunday when burglars vandalized three energy substations, power was then knocked out for even more homes after a suspect or suspects gained access to a fourth substation, vandalizing the equipment and causing a fire, according to an update from the Pierce County Sheriff's Department.The damaged equipment cut power to around 14,000 customers, police said, weeks after an attack in North Carolina left thousands in the dark for days amid federal warnings of extremist threats to electricity infrastructure.The Christmas Day vandalism near Tacoma marked more such incidents in the state, where two November attacks on Puget Sound Energy substations were investigated by the FBI.
Vandalism and deliberate damage were reported last month at substations in southern Washington and Oregon.No suspects are in custody in the latest case affecting Puyallup and Graham, Washington, and it "is unknown if there are any motives or if this was a coordinated attack on the power systems," the Pierce County Sheriff's Department said Sunday in a statement.The FBI's Seattle Division was aware of the vandalism reports but would not confirm or deny its role in any investigation, adding, "We do take threats against our infrastructure seriously and urge anyone with information to contact law enforcement," it told CNN on Sunday.The bureau in a November 22 bulletin warned of reports of threats to electricity infrastructure by people espousing racially or ethnically motivated extremist ideology "to create civil disorder and inspire further violence," according to the alert sent to private industry.Nothing taken in holiday incidentsThe first report of a burglary at a Tacoma.