Details on the cause of the problems were initially scarce, but the company confirmed that troubles in its frame relay network--one of several common technologies for transmitting data over telecommunications lines--were the source of the outages.
The problem also affected some Internet service providers that buy their Internet connections from Pacific Bell, which said their service went down around 8:30 a.m. PDT Friday. Some reported service returning by 12:30 p.m.
A Pacific Bell spokeswoman said that 911 services that tell operators the location of people calling were down earlier in the day, although calls were still getting through. That particular problem was mostly fixed by midday, she said.
Many high-speed DSL (digital subscriber line) customers were thrown offline, although the DSL technology itself was not at fault. Automatic teller machines, which often use frame relay connections, were also hard hit by the problem.
Abut 22,000 lines were initially affected, and by midday that number had been reduced to about 16,000, a Pacific Bell spokesman said.
The company hoped to have all lines back by late Friday night, he added. No information was immediately available on the cause of the problem.
"We're focused on restoring service for everyone as soon as possible," said spokesman John Britton. "But we'll be getting to the bottom of this as soon as we can."