Police departments and government officials across the country blamed AT&T Inc. for a 911 outage Wednesday night that prevented some people from contacting emergency responders for several hours.

Police in the District of Columbia said AT&T suffered a nationwide 911 outage for cellphone callers and asked residents in the nation’s capital to try a local number to report emergencies. Police in nearby Alexandria, Va., posted a similar message on Twitter, as did officials from Florida and Texas.

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