Further Reading FBI baffled over wave of nighttime fiber-optic cable vandalism

Vandalism on San Francisco Bay Area fiber optic cables is continuing, the Federal Bureau of Investigation said. Three lines were severed Tuesday, disrupting telecommunications service in the state's capital of Sacramento, and even as far north as Seattle.

The latest attack on an underground vault in Livermore, about 40 miles southeast of San Francisco, brings to 11 the number of separate incidents in the region dating to July 2014.

Greg Wuthrich, an FBI special agent in San Francisco, told Ars in a telephone interview that the agency was baffled, and the bureau has discovered "no real motive" for the cable cutting.

"These are vandalism cases at this point that are happening in multiple jurisdictions and in multiple cities," the agent said.

The lines are about as thick as a finger and are covered with flexible conduit. The cuts have been performed in areas where there are no security cameras.

The latest incident affected Internet wholesalers Level 3 Communications and Zayo Group Holdings. Internet, television, and phone service were impacted for a variety of service providers following the early morning Tuesday attack. Microsoft said there was a slowdown in its Azure cloud computing service because of cut fiber.

Wuthrich told Ars last month that those responsible "may appear to be normal telecommunications maintenance workers or possess tools consistent with that job role."