Cellphone outages are being reported nationwide Thursday, Feb. 22. File photo.

AT&T said Thursday afternoon 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. “We sincerely apologize to them.”

Thursday morning, a number of Americans were dealing with cellular outages on AT&T, according to data from Downdetector. AT&T had more than 73,000 outages around 9:30 a.m., in locations including Pittsburgh, Houston, Atlanta and Chicago. The outages began at about 3:30 a.m. The carrier has more than 240 million subscribers, the country's largest.

“Some of our customers are experiencing wireless service interruptions this morning. We are working urgently to restore service to them. We encourage the use of Wi-Fi calling until service is restored,” AT&T said in a statement Thursday morning.

Cricket Wireless, owned by AT&T, had more than 13,000, the outage tracking website said Thursday.

“Verizon’s network is operating normally. Some customers experienced issues this morning when calling or texting with customers served by another carrier. We are continuing to monitor the situation,” Verizon said.

T-Mobile said that it did not experience an outage.

“Our network is operating normally. Downdetector is likely reflecting challenges our customers were having attempting to connect to users on other networks,” T-Mobile said.

Some iPhone users had seen “SOS” displayed in the status bar on their cellphones. The message indicates that the device is having trouble connecting to their cellular provider's network, but it can make emergency calls through other carrier networks, according to Apple Support.

So far, no reason has been given for the outage.

Downdetector.com is a website that collects data through cellular user reports of outages.

According to Butler County dispatcher Deb Bell on Thursday morning, the outage should not affect the ability to make emergency calls.

“We’ve not been having any problems,” she said. “We’ve had our phone crew here running test calls all morning.”

Eagle staff writer Molly Miller contributed to this report.