A cellular outage has swept across large portions of the US, causing disruptions in services provided by major telecom companies including AT&T, Verizon, and T-Mobile.

Data collected from outage tracking website Downdetector revealed that more than 32,000 incidents were reported with AT&T's service around 4:30am Eastern Time. The outage affected cities including San Francisco, Houston, and Chicago, according to information displayed on the website.

Users of...