(CNN) AT&T wireless customers in several states were unable to make calls to 911 on Wednesday.

The outage was resolved by Wednesday night, according to AT&T, but it had affected customers from coast to coast.

Issue has been resolved that affected some calls to 911 from wireless customers. We apologize to those who were affected. — AT&T (@ATT) March 9, 2017

Ajit Pai, chairman of the Federal Communications Commission, tweeted that his staff was investigating the incident.

We're receiving reports of widespread AT&T 911 call outages. @FCC public safety staff are investigating. I'll post more info once available. — Ajit Pai (@AjitPaiFCC) March 9, 2017

"We're receiving reports of widespread AT&T 911 call outages. @FCC public safety staff are investigating. I'll post more info once available."

Police departments across the United States were reporting outages. They used social media to urge people to call departments' main telephone lines instead of 911.

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