AT&T and Verizon have it managed to resolve an outage that left customers unable to reach 911, make calls or use the internet.
At least 24 states were experiencing problems that plagued thousands of Americans from North Dakota to Illinois and New York.
DownDetector, a site that monitors online outages, showed AT&T disruptions occurred around 12:26pm ET, but skyrocketed about four hours later, and Verizon experiencing issues throughout the day.
Customers reported dropped calls and an inability to hear the person on the other end of the line.
AT&T said that they had managed to resolve the issue shortly after 8pm ET, while Verizon said their network was working normally - with only users in the Northeast and Midwest experiencing issues.
This is the second major cellular outage for the year amid growing warnings that hackers are targeting US infrastructure.
AT&T customers have reported issues making 911 calls in multiple US states. At least 24 states are experiencing problems that started around 12:26pm ET
An AT&T statement said: 'We are not experiencing a nationwide outage, but we are aware of an issue that is affecting the ability of some customers to complete cellular calls between carriers.
'We are working collaboratively among affected carriers to determine the quickest path to resolution.
'The issue disrupting calls between carriers has been resolved. We collaborated with the other carrier to find a solution and appreciate our customers patience during this period.'
While the AT&T glitch started in the afternoon, DownDetector received issue reports about Verizon throughout the day.
User reports about Verizon's issues were largely concentrated in the Northeast, including New York, Boston, but also Chicago, Detroit and Seattle appear to be impacted.
However, a Verizon spokesperson told DailyMail.com that its 'network is operating normally,' noting the issue reports are from 'calling or texting with customers served by another carrier.'
The spokesperson said the company is 'monitoring the situation.'
AT&T issues haD been reported across the nation - Tampa, Atlanta, Houston, Los Angeles and Phoenix are experiencing problems.
What is causing the issues and how many people have been impacted are not yet known.
Customers of AT&T and Verizon cited problems with 'mobile phone,' 'mobile internet' and 'landline internet,' according to DownDetector.
Those unable to reach 911 should contact their local emergency services directly.
DownDetector, a site that monitors online outages , shows disruptions occurred around 12:26pm ET, but skyrocketed about four hours later
User reports about Verizon's outage are largely concentrated in the Northeast, including New York, Boston, but also Chicago, Detroit and Seattle appear to be impacted
AT&T, however, is more spread out with issues in Tampa, Atlanta, Houston, Los Angeles and Phoenix
AT&T responded to a frustrated customer on X who posted: 'So is it an issue or all cell phones? I can’t get a call to go thru to another carrier except ATT.'
The cellular company replied: 'Let's help find out what's causing this. Please DM us your ZIP code and we'll get down to work.'
AT&T has a service dashboard that lets users see if there is an outage in their area.
A Verizon customer posted on X: '@VerizonSupport 120$ a month for Verizon to be down.'
'We would love to take a closer look into your service concerns. Please DM us,' a company spokesperson replied to the post.
One AT&T customer shared on X that her service 'is fine,' but her husband's Verizon has been down most of the day.
Verizon experienced its last outage in January, which lasted for about four hours, but AT&T has been hit with problems several times in the last few months.
The most recent occurred on May 22, but only impacted customers in Virginia and North Carolina due to a down tower in the area.
AT&Twent down in February - an outage that hit at least 70,000 Americans for up to 12 hours. Customers lined up at stores during the incident to get answers about having no service
But the cellular company went down in February - an outage that hit at least 70,000 Americans for up to 12 hours.
AT&T blamed issues on a 'software glitch' and told customers who were impacted that they would receive a $5 credit to their next bill.
'Based on our initial review, we believe that today's outage was caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack,' AT&T said.
'We are continuing our assessment of [the] outage to ensure we keep delivering the service that our customers deserve.'
However, the incident was so widespread it caught the attention ofthe Department of Homeland Security (DHS) and FBI that opened an investigation into the outage.
Cyber experts told DailyMail.com that the February issue had hallmarks of a cyberattack, potentially an attempt by hackers to blackmail the company or steal user data.
The widespread nature, according to experts, seemed similar to 'a massive Distributed Denial of Services (DDOS) attack on core Internet infrastructure.'
Using DDOS, cybercriminals are attempting to crash a website or online service by bombarding it with a torrent of superfluous requests at exactly the same time.
The surge of simple requests overload the servers, causing them to become overwhelmed and shut down.
But the U.S. Cybersecurity and Infrastructure Security Agency (CISA) had reported that 'the cause of the outage [was] unknown and there are no indications of malicious activity.'
