NEW YORK (AP) — Some Verizon customers in the U.S. were hit by a service outage Monday.

The problem appeared to knock out cell phone service for tens of thousands of Verizon users. Data from outage tracker DownDetector shows that the number of reports reached the 100,000 mark shortly after 11 a.m. ET — and while that number dropped significantly, nearly 48,000 were still experiencing issues around 4 p.m. ET.

Frustrated users shared online that they were without service in many parts of the country, including the southeastern US, where residents are still reeling from the aftermath of Hurricane Helene. But the outage is not limited 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 may have experienced today.” The company added that while service has been restored to many customers, technicians continue to work to fully resolve this issue.

Also the Federal Communications Commission recognized the outage later in the day, but provided no further details other than to say the cause was being investigated.

Some Verizon iPhone customers were seeing SOS messages displayed in the status bar on their cell phones. The message indicates that the device is having trouble connecting to the mobile carrier’s network, but can make emergency calls over other carriers’ networks.

During cell such service disruptionsan alternative is to connect to nearby WiFi. Wi-Fi calling is also a built-in feature on most Android devices and iPhones and can be enabled through the phone settings.