RICHMOND, Va. — A state commission says the 911 outage in Northern Virginia after last summer’s derecho was caused by Verizon’s failure to perform necessary maintenance.

The State Corporation Commission said in a final report issued Thursday that the 911 failure was compounded by Verizon’s failure to monitor and respond to the outages.

The June 29 storm included near-hurricane-force winds and caused millions of people to lose electricity. It knocked out power to a Verizon facility in Arlington that resulted in 911 calls not working in Arlington, Fairfax and Prince William counties and the city of Manassas — an area with a population of more than 1.7 million.

The commission said Verizon has taken corrective action. Verizon said in a statement that it will continue to improve its network’s resiliency.

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