Some Verizon customers across the U.S. were hit by a service outage Monday.

The issue appeared to knock out cellphone service for tens of thousands of Verizon users. Data from outage tracker DownDetector shows that reports topped 100,000 shortly after 11 a.m. ET — and while that number dropped significantly, nearly 48,000 were still facing issues closer to 4 p.m. ET.

Frustrated users online shared that they didn't have service in many parts of the country — including the Southeastern U.S., where residents are still reeling from the aftermath of Hurricane Helene. But the outage wasn't isolated to one region. DownDetector's map also showed many reports coming from the West Coast, Midwest and Northeast.

A statement from New York-based Verizon confirmed the issue with its network and apologized “for any inconvenience some of our customers experienced today.” The company added while service has been restored for many customers, its engineers are continuing to work to fully resolve this issue.

The Federal Communications Commission also acknowledged the outage later in the day, but didn't provide further details beyond saying it was looking to determine the cause.

Some Verizon iPhone customers saw SOS messages 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.

During cell service outages like this, one alternative is connecting to nearby Wi-Fi. Wi-Fi calling is also a built-in feature on most Android devices and iPhones and can be turned on under the phone’s settings.