Oakland Fire Department’s 911 system was also affected. During the outage, emergency calls were routed to the Alameda County Sheriff’s Office, while Oakland police said officers would respond only to Priority 1 calls, such as reports of violence or an immediate threat of death or serious injury.

The disruption has raised questions about why the city’s backup systems did not keep emergency communications operating. Police Chief James Beere said at a Thursday news conference that two initial fallback plans for 911 were compromised, forcing the city to turn to Alameda County. The police department declined a request for a follow-up interview Friday, citing an active investigation.

AT&T told investigators that damage to its fiber and copper lines caused the interruption. Beere said the number of affected lines and the extent of the damage suggested the incident may have involved more than ordinary vandalism, but officials have not publicly established who caused it or why.

The outage also highlighted the risks of relying on vulnerable communications infrastructure during a disaster. Mark Benthien of the Statewide California Earthquake Center said residents should not expect phone service to be available after a major earthquake. Angie Lux of the Berkeley Seismology Laboratory said severe earthquake damage could leave communications systems down for days or weeks.

Lux described the Oakland disruption as a troubling example of what could happen on a much larger scale after an earthquake. Benthien urged residents to prepare by getting to know neighbors and identifying resources in their communities.

With services restored, key questions remain: why both of Oakland’s initial 911 fallback options failed, how the damaged lines were protected, and what changes could prevent a similar outage. The incident interrupted emergency response communications across the city for more than a day, underscoring the importance of reliable backup systems as well as neighborhood-level preparedness.