AT&T said Thursday its wireless network was back after an outage knocked out cellphone service for its users across the U.S. for hours.

"We have restored wireless service to all our affected customers," the Dallas-based company said in a statement posted on its website Thursday afternoon. "We sincerely apologize to them."

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Outage tracker Downdetector noted that outages, which began at about 3:30 a.m. ET, peaked at around 73,000 reported incidents. AT&T had more than 58,000 outages around noon ET, in locations including Houston, Atlanta and Chicago. The carrier has more than 240 million subscribers, the country's largest.

By 3:30 p.m. ET, the reports were down to fewer than 3,000.