The Washington Emergency Management Division believes the 911 system is stable now, but it still wants assurances from CenturyLink there won't be a repeat of Thursday's statewide outage.
Division Director Robert Ezelle says the phone company shared some information Monday as it investigates what went wrong.
Ezelle said Tuesday the state still wants to pin down why backup system didn't kick in.
CenturyLink says about 4,500 calls failed to get through during a six-hour outage caused by a technical error in a third-party vendor's call router. About 770 calls were completed in that period. CenturyLink says it has addressed the issue.
The outage involved 127 dispatch points in Washington.
The company says a similar two-hour 911 outage in parts of northwest Oregon was caused by a separate problem.