In Salon yesterday, reporter Kim Zetter penned a story describing allegations by two unnamed sources that the federal government has set up a facility in a closed-off room inside an AT&T “network operations center” in St. Louis — a site that plays a major role in managing all of AT&T’s Internet operations. According to Zetter, the site is the “technical command center from which the company manages all the routers and circuits carrying the company’s domestic and international Internet traffic. Therefore, [the site] could be instrumental for conducting surveillance or collecting data.”

We’ve heard a bit about this before. Back in January, Mark Klein, a former AT&T technician, became a witness in a class-action lawsuit filed by the Electronic Frontier Foundation against AT&T, charging the company with illegally taking part in a NSA domestic-surveillance program. Klein alleged the existence of government surveillance operations in AT&T offices in San Francisco an in Bridgeton, Missouri, near St. Louis, according to AT&T documents.

Zetter’s Salon story cites two sources who worked at the Bridgeton facility but who had never actually entered in the room in question, or even — amazingly — asked the people who worked in it what they were doing, even though the sources had been told by others at the company that “employees working inside the room were ‘monitoring network traffic’ and that the room was being used by ‘a government agency.’”

From there, Zetter — who has won several awards for her investigative and feature reporting — builds a case about what could be going on in the room, which leads to a story populated with more than its fair share of “could be’s” and “might’s,” with a frustrating lack of concrete evidence to confirm the suspicions of the employees, technology experts and former NSA hands she speaks to, all of whom say the operation smells like an NSA program.

“If the NSA is using the secret room,” she writes, “it would appear to bolster recent allegations that the agency has been conducting broad and possibly illegal domestic surveillance and data collection operations …”

Later, there’s this: “The nature of the government operation using the Bridgeton room remains unknown, and could be legal. Aside from surveillance or data collection, the room could conceivably house a federal law enforcement operation, a classified research project, or some other unknown government operation.”

The piece also quotes “NSA expert Matthew Aid, who has spent the last decade researching a forthcoming three-volume history of the agency,” saying: “I’m not a betting man, but if I had to plunk $100 down, I’d say it’s safe that it’s NSA.”

Later, Zetter writes, “It’s possible the Bridgeton room is being used for a federal law enforcement operation … it is also possible that the Bridgeton room is being used for a classified government project, such as data mining, with which the Pentagon has experimented in the past.”

And she tells us that workers at the AT&T center “could conceivably collect data using any AT&T router around the country…To do so, the company would need to install a wiretap-like device at select locations for ‘sniffing’ the desired data.”

All of which builds a case, and raises questions, but never quite delivers the goods. Phrasing the story in this way was intentional, Zetter told CJR Daily, since her sources had never been inside the tightly-controlled room, but were told by “company supervisors” that company employees inside the room were working on a government project. She says that all of the informed speculation in the story were her and her editor’s way of “hedging our bets,” about what is going on at the AT&T facility, but that they are confident about the finished piece.

Given the New York Times’ James Risen and Eric Lichtblau’s account of alleged NSA eavesdropping on phone calls back in December and Leslie Cauley’s May piece in USA Today accusing AT&T, Verizon and BellSouth of handing phone records over to the NSA (which the companies have either denied or declined to comment on) there’s plenty of circumstantial evidence that suggests Zetter could be right.

But just like the sources for those other stories, Zetter’s anonymous sources stand to lose their livelihoods if they’re outed, which sets up a frustrating cat-and-mouse game for the reader — if we don’t know who these people are, and what their motivations might be, how can we judge the veracity of their claims?

Zetter told CJR Daily that she had other sources who refused go on record, even anonymously, and she declined to divulge how she goes about finding and assessing her anonymous sources.

Paul McLeary is senior editor of Defense Technology International magazine, and is a former CJR staffer.