Authorities said three electricity substations in the Tacoma, Washington, area were attacked on Sunday, affecting up to 14,000 customers.
The Pierce County Sheriff’s Department described the early morning attacks on two Tacoma Public Utilities substations and a Puget Sound Energy facility as vandalism, with the perpetrators still unknown.
“It is unknown whether there are any motives or if this was a coordinated attack on the power systems,” said the sheriff’s department in a statement.
At one point on Sunday, the agency estimated that 14,000 homes and businesses were affected.
Tacoma Public Utilities reported that more than 7,000 of its customers in Graham and Elk Plain were without power on Sunday, and that restoration efforts were ongoing late in the day.
Puget Sound Energy reported on its website that more than 1,200 customers were without power on Sunday, with the vast majority of them restored, but it was unclear whether this was related to the attack. It did not respond immediately to a request for comment.
Many of those TPU customers appear to have had their power restored; the national blackout tracker PowerOutage.us reported late Sunday afternoon that only about 5,000 customers remained without power across the state.
“Two of our substations were deliberately targeted by physical attacks,” TPU said in a statement.
The sheriff’s department stated that in each of the attacks, a person or people broke into facilities and vandalised equipment, the first of which was reported at 2:39 a.m.
TPU stated that federal law enforcement alerted it to the possibility of an attack earlier this month and recommended a security assessment. It refused to say what steps, if any, it took.
At the same time, Oregon Public Broadcasting and Seattle’s KUOW public radio reported separate attacks in mid-November on six substations operated by Portland General Electric, the Bonneville Power Administration, the Cowlitz County Public Utility District, and Puget Sound Energy in Washington and Oregon. According to the reports, the incidents included violations of utility properties.
Vandals attacked two Duke Energy substations in Moore County, North Carolina, on December 3, leaving 45,000 customers without power for more than three days, according to officials. People armed with firearms opened fire and, in one case, broke into a facility, they claimed, and they remained at large nearly a month later.
As the last North Carolina customers’ power was restored on December 7, someone opened fire near a Duke Energy hydro facility in Ridgeway, South Carolina, about 130 miles south of Moore County. Federal investigators were comparing ballistics evidence from both attacks to see if they were linked.
Investigators looking into the North Carolina attacks were looking at online conspiracy theories to see if any played a role, according to two senior law enforcement officials briefed on the situation this month.
One popular theory was that the outages were staged to disrupt a drag show called “Downtown Divas” at the Sunrise Theater in Southern Pines, North Carolina. In the days leading up to the Saturday night event, anti-LGBTQ protesters targeted the location, which continued in the dark before ending early.
White supremacists and other right-wing extremists seeking American “destabilisation” have long targeted power infrastructure, according to Brian Levin, director of the Center for the Study of Hate and Extremism at California State University, San Bernardino, in February.
Three men pleaded guilty earlier this year in connection with a plot to disrupt the electricity grid, sow civil unrest and economic uncertainty, and eventually spark a race war, federal prosecutors said at the time.
There is no evidence that the attacks in Washington, Oregon, and the Carolinas were motivated similarly. The Tacoma-area attacks on Saturday were still being investigated.