The company, based in Philaedelphia, is reportedly the second largest broadcasting and cable television firm in the world.
Comcast's technical support team tweeted that the issue was caused by fiber cut that was also believed to be impacting other providers. Some reported difficulty getting through to Comcast customer service.
In a series of posts responding to customers, Comcast said one of its large backbone network partners had a "fiber cut" that's affecting service nationwide.
The shares were up 1.5 percent to $33.11 at 3:22 p.m.in NY.
Comcast customers across the United States experienced a massive internet, cable TV, and telephone outage on Friday.
A nationwide outage with Comcast impacted police phone lines in Petersburg on Friday.
Update: I'm told the problems on the Chicago to NY route have been resolved, and many Comcast customers should soon see services restored.