SAN FRANCISCO (CBS SF) — PG&E and fire officials in San Francisco were reporting rolling blackouts that were affecting thousands of customers across the city Thursday morning.

PG&E confirmed that the outages cut power to about 5,900 customers across the city at about 10:30 a.m. By shortly before 12 p.m., all power had been restored.

PG&E officials said they did not know what was causing the power to go out.

The San Francisco Fire Department said the outages were tripping false fire alarms that were occupying many of the department’s first responders.