Screenshot by Lori Grunin/CNET

If you couldn't reach your favorite websites Friday at about 12:30 p.m. ET, it wasn't just you.

Subscribers of Comcast's Xfinity TV, internet and phone services around the country took to Twitter with complaints about outages. Downdetector's graphs displayed the same spike in complaints from almost every site it monitors. The graphs soon began to retreat to normal levels. Whew!

We asked a handful of major broadband providers if they could shed some light on what happened. Comcast got back to us this evening with the following statement:

"We identified two, separate and unrelated fiber cuts to our network backbone providers. Our engineers worked to address the issue immediately and services are now being restored to business and residential internet, video and voice customers. We again apologize to anyone who was impacted."

However, major backbone provider CenturyLink, which owns Level 3 Communications, responded to us saying it hadn't had any issues and that its lines were not compromised -- rumors had been circulating to the contrary. So it still remains unclear as to who those affected backbone providers were.

Update, 4:56p.m. PT: CenturyLink has revised its statement, now telling CNET that it has also experienced two fiber cuts. We're working to understand if they're the same as the ones that affected Comcast. Here's the statement:

While the CenturyLink network continues to operate normally, on June 29, we experienced two isolated fiber cuts in North Carolina affecting some customers that by themselves did not cause the issues experienced by other providers. At this time, our technicians are working to restore the services.

Update, 5:16p.m. PT: Comcast tells CNET that CenturyLink was indeed one of the internet backbone providers responsible for the fibers that were cut. The other was Zayo. Comcast believes they're isolated incidents, but both cuts were partially responsible for the outage.

"Earlier today, Zayo experienced a fiber cut in the New York area. We immediately dispatched our local team who quickly restored the cut. All impacted services in the area have been restored," a Zayo spokesperson told CNET.

AT&T and Verizon spokesmen said their companies were not aware of any impact on their networks.

We'd known about the fiber-line cut since about 2:13 p.m. ET, when Joan Gralla from Newsday tweeted out that "Comcast is experiencing a national outage due to 2 fiber line cuts. One between NYC & Chicago, the second between Ashburn & South Carolina."

NY| Manhattan| *Communication Failure*| 30 Rockefeller Plaza (Comast)| Comcast is experiencing a National outage due to 2 fiber line cuts. One between NYC & Chicago, the second between Ashburn & South Carolina. customers urged NOT TO CALL 911, no ETA on a fix, police monitor — Joan Gralla (@JoanGralla) June 29, 2018

Because Comcast supplies internet backbone to a lot of places, it took 'em all out.

Just a few minutes later, all of Comcast's official central and regional accounts tweeted out: "One of Comcast's large backbone network partners had a fiber cut that we believe is also impacting other providers. It is currently affecting our business and residential internet, video and voice customers. We apologize & are working to get services restored as soon as possible."

First published at 10:52 p.m. PT Friday.

Update, 3 p.m. PT: Reorganized and rewritten for clarity and to add comments.

Update, 5:29 p.m. PT: Added new statements.

CNET's Sean Hollister contributed to this story.