Three power substation facilities were vandalized in Pierce County, Washington, on Christmas morning, knocking out power to more than 14,000 customers, authorities said.

Two of the break-ins were at Tacoma Public Utilities substations and the third was at a Puget Sound Energy station, according to the sheriff’s office in Pierce County, which encompasses Tacoma.

No suspects are in custody, according to the sheriff’s office.

“It is unknown if there are any motives or if this was a coordinated attack on the power systems,” the sheriff’s office said in a statement.

Tacoma Public Utilities said about 2,000 of its customers are still without power and crews are working on restoration.

The Department of Homeland Security issued a bulletin last month warning that U.S. critical infrastructure could be among the targets of possible attacks by “lone offenders and small groups motivated by a range of ideological beliefs and/or personal grievances.”

Earlier this month, two electrical substations were shot up in North Carolina, causing tens of thousands of customers to lose power and prompting local officials to declare a state of emergency.