Vandals severed underground fiber-optic cables in Livermore and disrupted cable and Internet service in the Sacramento area, the 11th such case in Northern California in the past year, authorities said Wednesday. The cables that were vandalized are owned by Level 3 Communications and Zayo, and Wave Broadband is a customer of those two companies, said Wave Broadband spokesman Mark Peterson. FBI officials in Sacramento disputed a statement issued by Wave Broadband that described the vandalism as a widespread “coordinated attack.” The FBI is coordinating the investigation, which involves several local law enforcement agencies, Wuthrich said. The cases are not related to a mysterious rifle attack on a Pacific Gas and Electric Co. substation near San Jose on April 16, 2013, that damaged 17 transformers and caused $15 million in damage, authorities said. In April 2009, vandals cut underground fiber-optic cables at four sites, knocking out landlines, cell phones and Internet service for tens of thousands of people in Santa Clara, Santa Cruz and San Benito counties.