The mobile phone alert, which was also mistakenly sent to people in OR, urged people to call a number with a 360 area code. CRESA said it pushed information about reaching 911 through "all other methods" before sending a message through its Emergency Alert System and Wireless Emergency Alerts systems Thursday evening.
Jessica Rosenworcel, a member of the Federal Communications Commission, said via Twitter it was a nationwide outage and her agency needed to investigate.
CenturyLink says customers have not been able to file trouble reports online.
The outage also did not affect text-to-911 in all areas where that feature is available.
The Iowa State Patrol said a county's 911 cellphone calls were being routed to the agency's office in Des Moines.
Officials in Jefferson Co. told 13 NEWS they were receiving reports of outages in the area.
"CenturyLink engineers and technicians have identified a network element that was impacting customer services and are addressing the issue in order to fully restore services".
Verizon said it had service interruptions in Albuquerque, New Mexico, and parts of Montana as a result of issues with CenturyLink. It's unclear if and how the CenturyLink problems were related to the 911 outage, but tweets from the Seattle Police Department and Clark County 911 Dispatch indicated that they were connected. Verizon said CenturyLink helps handle wireless network data traffic for Verizon and other wireless providers.