ST. PAUL, Minn. (AP) — Officials in Minnesota said Thursday that a third-party vendor performing work on a 911 system led to widespread service failures across the state, with similar disruptions reported in North Dakota and North Carolina.

The outage saw several cities and counties scramble to broadcast alternative emergency phone numbers through social media and other means during the hourlong disruption Wednesday afternoon. Telecommunications company CenturyLink, which operates 911 networks in the three states, said it’s investigating how the vendor’s work led to the outage.

Minnesota’s Emergency Communications Networks Director Dana Wahlberg said some callers were still able to reach emergency services during the interruption before service returned to normal at 5:30 p.m. Wednesday. The department said it’s reviewing how many of the state’s 102 emergency centers were impacted.

Wahlberg said she expects 911 to work because it “is a vital service not only in Minnesota but across the nation.”

CenturyLink Spokesman Frank Tutalo confirmed in a brief statement Thursday that a third-party vendor’s work impacted 911 services. He did not immediately return messages seeking comment on the vendor and the scope of the outage.

CenturyLink has been Minnesota’s emergency network provider for the past seven years and is in its second year of a five-year contract.

In 2015, the Federal Communications Commission fined the company $16 million for a six-hour 911 outage in 2014 that affected more than 10 million people in Minnesota, Washington and North Carolina.

Emergency network contractors are required to submit a report within 14 business days after an outage.

“We will expect concrete data to guide us to understanding what the issue was,” Wahlberg said.