AT&T says a nationwide outage that prevented wireless customers from making 911 emergency calls has been resolved.

“Service has been restored for wireless customers affected by an issue connecting to 911. We apologize to those affected," company officials said in the statement.

At this time, the reason behind the outage has not been revealed.

Several police departments throughout Texas have sent out messages on Twitter about the outage, including Houston Police Chief Art Acevedo.

Agencies in Florida, Tennessee and Washington, D.C, have also sent out tweets saying they've been affected by the outage and are providing different numbers to call.