Comcast (CMCSA) experienced a major service interruption on Monday that affected wide swaths of the country. The Downdetector.com outage tracker shows major cities in the Northeast Corridor—from Washington, D.C. to Boston—affected, as well as Detroit, Chicago, Atlanta, San Francisco, Denver, Houston, Seattle and Portland, along with several smaller cities.

Downdetector notes the problems seem to have started around 6:30 a.m. Eastern on Monday. Twenty-six percent of the complaints it received pertained to a total blackout of services.

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Comcast did not formally acknowledge the problem until 12:30 p.m. Eastern, though, when it said in a statement that it was “continuing to investigate what appears to be a temporary network interruption that impacted some of our services”. About an hour later, the company said it had “repaired the temporary network interruption that impacted some of our services this morning. Our engineers continue to work on this issue and almost all services have already been restored.”

Customers, on Twitter, vented at the company. Some said they had experienced outages of roughly five hours and others saying over an hour after Comcast sounded the all clear that their service had still not been repaired.

Adding to the company’s customer service woes, the volume of incoming calls seemingly overwhelmed the call centers, with many customers saying they were unable to get through to live support operators.

https://twitter.com/numlask/status/699307762019385344

The company’s Twitter account, though, was especially active as reps tried to keep up with the flow of complaints.

@SarGar08 Mondays….ugh… seriously though, we are working on fixing this as fast as possible, very sorry for the issues / delay – PL

— Xfinity Support (@XfinitySupport) February 15, 2016

Beyond the two statements on its corporate site, Comcast has not offered any additional information behind the cause of the outages.