The FBI is working with police to catch vandals behind nearly a dozen fiber-optic cable cuts in Northern California in the past year.
The latest snips occurred Tuesday, when someone sliced at least three fiber-optic cables in an underground vault in Alameda County east of San Francisco. The cuts disrupted Internet and phone service around Sacramento for 20 hours before service was restored.
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FBI spokesman Greg Wuthrich says the FBI has known about the separate vandalism incidents and became involved last month because cable cuts in one location can affect businesses and customers in other cities and counties, requiring coordination.
The FBI says fiber cables in Fremont, Berkeley and San Jose have been intentionally severed in 11 instances since July 2014.
Federal officials say there is no evidence that the San Francisco Bay Area acts are linked with the sabotage of a Pacific Gas & Electric Co. substation in April 2013. The nighttime attack knocked out phone and emergency 911 service in Silicon Valley.
Wuthrich declined to say how many companies and customers were affected by the cable snips this week.
"It's something local and it's vandalism," he said.
Asked if the incident might be part of a broader and sophisticated attack, Wuthrich said, "We're not going in that direction."
Customers of Wave Broadband experienced phone loss and a slow Internet Tuesday. The Kirkland, Washington, company provides Internet, telephone and television links through cables to customers in Oregon, Washington and California.
"It was not a network-wide outage," said spokesman Mark Peterson. "It was confined to some customers in and around suburban areas of Sacramento."
He said the fiber cables affected are not owned by Wave Broadband, but by two Internet backbone providers, Level 3 Communications and Zayo.
The FBI is seeking help from the public.
A press release warns that vandals "may appear to be normal telecommunications maintenance workers or possess tools consistent" with telecom maintenance work.