AT&T Corp. set up a special room at one of its internet facilities in 2003 that was open only to employees cleared by the US National Security Agency (NSA), according to a declaration by a retired engineer as part of a lawsuit over alleged mass invasion of privacy by the carrier.

That document was unsealed on Thursday after a deal was reached between AT&T Inc, the new owner of the long-distance company, and the Electronic Frontier Foundation (EFF), which is suing on behalf of AT&T customers.

The EFF wants everything in the documents made public, while AT&T wanted it all sealed, saying exposure would reveal trade secrets.

The EFF alleges AT&T gave the government phone call records and real-time information on internet use without the government producing a warrant or other required authority. The data-gathering process was begun as part of antiterrorist measures after the September 11, 2001 terrorist attacks, the civil-rights group said. Its suit is one of several class actions against carriers for alleged illegal cooperation with federal antiterrorist surveillance. AT&T and the Department of Justice want the case dismissed.

The declaration made public Thursday was given to EFF on March 28 by Mark Klein, who said he retired from the carrier in 2004 after working there for 22 years. The group presented the papers to support a motion for a preliminary injunction to stop the alleged spying. Key words and sentences in Klein's declaration are redacted, or blacked out.

According to the remaining text, Klein worked at a facility in 2002 that provided WorldNet Internet service, domestic and international VOIP (voice over Internet Protocol) and data transport service to the Asia-Pacific region. That year, he was told an NSA agent came to the facility to interview an employee for a special job at another facility. While touring that facility in January 2003, Klein saw a special room being built and near completion.

Later in the declaration, KIein discusses technology for physically splitting fibre in order to monitor communications going over fibre-optic circuits. Klein said he was responsible for installation and troubleshooting of fibre-optic circuits.

In addition to Klein's declaration, the EFF's motion for the injunction was made public Thursday. In the declaration, Klein referred to other documents, which were not made public.

On Monday, Wired News published a statement and documents attributed to Klein that describe a secret room at an AT&T central office in San Francisco where the carrier tapped into lines used for internet service.