SONORA (CBS13) – City and county authorities are warning residents in Tuolumne County that they’re experiencing widespread cellphone and landline outages, but 911 service is not affected.

The problems started a little after 1 a.m. Thursday, according to the Sonora Police Department.

It appears most city and county landlines can still call 911, but the emergency calls have to be routed through the police department.

Sonora police urge residents to still call 911 in an emergency.

AT&T is investigating the issue. Exactly what’s causing the problem is unclear and an estimated time of repair has not been given.