Updated at 3:10 p.m. to include a statement from AT&T.

A nondescript, square brick building owned by AT&T in Old East Dallas is among several fortress-like structures in major U.S. cities being used to eavesdrop on Americans by the National Security Agency, The Intercept has reported.

The Intercept said in its June 25 report that the boxy building at 4211 Bryan St. houses sophisticated telecommunications networking equipment that the NSA uses for its controversial warrant-less surveillance program.

The online news publication said it relied on classified NSA documents to identify similar AT&T facilities in Atlanta, Chicago, Los Angeles, New York City, San Francisco, Seattle and Washington, D.C.

The Intercept also cited "public records and interviews with several former AT&T employees" as sources in its report.

AT&T released the following statement Wednesday afternoon:

"Like all companies, we are required by law to provide information to government and law enforcement entities by complying with court orders, subpoenas, lawful discovery requests and other legal requirements. And, we provide voluntary assistance to law enforcement when a person's life is in danger and in other immediate, emergency situations. In all cases, we ensure that requests for assistance are valid and that we act in compliance with the law."

An AT&T spokesman also said the company has a transparency report.

The equipment the buildings house "transports large quantities of internet traffic across the United States and the world," the publication said.

The building on Bryan Street, built in 1961, has small nontransparent windows and large vents but few other features that make it stand out.

AT&T corporate headquarters in downtown Dallas, Wednesday, September 13, 2017, in Dallas. (David Woo / Staff Photographer)

The NSA's spying initiative has for years monitored phone calls, emails, text messages and other communications belonging to Americans under the stated goal of protecting national security.

The agency said last year in response to concerns from members of Congress that it will focus on internet communications sent directly to or from a foreign target. The NSA also said it will no longer monitor communications between two people who are not targets of surveillance.

The Intercept said in its report that the NSA "considers AT&T to be one of its most trusted partners" due to the company's willingness to help.

The NSA also values its partnership with AT&T because the telecom giant "maintains unique relationships with other phone and internet providers," according to The Intercept.

"The NSA exploits these relationships for surveillance purposes, commandeering AT&T's massive infrastructure and using it as a platform to covertly tap into communications processed by other companies," the online publication said in its report.

The Intercept report cites NSA and AT&T maps as identifying the Bryan Street building as being one of eight "peering" hubs in the U.S. that "process internet traffic" as part of an NSA surveillance program.

"NSA documents explicitly describe tapping into flows of data at all eight of these sites," the news report said.