Interruptions to US mobile services have been reported across the United States on Thursday morning.
Downdetector.com, which tracks outages, showed thousands of reports made by users of multiple networks after 04:00 EST (09:00 GMT).
Tens of thousands of reports have been sent for AT&T - with hotspots in the south and east, Downdetector says.
Users say their phones are displaying the SOS message, leaving them unable to make calls or access services.
The cause is unclear. The BBC has approached several operators for comment.
AT&T is responding to customer complaints online but has not yet widespread acknowledged network problems.
Verizon - one of the networks that has received reports on Downdetector - told the BBC its network was operating normally.
It suggested customers were logging issues after making unsuccessful attempts to contact users of another provider.
T-Mobile said its network is also working as normal and customers reporting issues may be having trouble making outgoing calls to another network.
A few thousand customers with Cricket Wireless, UScellular and Consumer Cellular are also reporting issues.
Users are having issues with calls, texts and internet access, with most reports indicating no service or no signal.
Downdetector's heatmap shows major population centres including Los Angeles, Chicago, Houston and Atlanta are among those facing the highest number of outages.
911 emergency service is also down in some areas, with officials advising the use of a landline, social media or a cell phone with a different carrier in the event of an emergency.
Latest Stories
-
Financial inclusion key to Africa’s development – Deputy Governor of BOG
1 min -
WAFU B U-17 Cup of Nations: Our game plan worked perfectly – Laryea Kingston
11 mins -
Akufo-Addo government spending money as if there’s no tomorrow – Minority Leader
42 mins -
Two rainstorms heading for Ghana – GMet warns
54 mins -
Ashanti Region: Policeman found dead with gunshot wounds in Bobiri Forest
54 mins -
Today’s front pages: Thursday, May 16, 2024
59 mins -
We’ll involve traditional leaders in the granting of mining licenses – Mahama
1 hour -
Cedi depreciation: Watch how $1 reached GH₵15
1 hour -
‘NPP will peacefully hand over and walk away when defeated’- Henry Quartey
1 hour -
Trades Minister stops cement price hikes
2 hours -
Fidelity Bank joins forces with Proxtera to empower Ghana’s SMEs on GIFE Platform
2 hours -
Biden’s personal finances little changed in 2023, documents show
3 hours -
Palmer scores as Chelsea beat Brighton to go sixth
3 hours -
Hojlund seals thrilling Man United win over Newcastle
3 hours -
Juventus beat Atalanta to win Coppa Italia
3 hours