Technology companies stung by the controversy over the National Security Agency's sweeping Internet surveillance program are calling on U.S. officials to ease the secrecy surrounding national security investigations and lift long-standing gag orders covering the nature and extent of information collected about Internet users.

The requests, made by Google, Facebook and Microsoft and echoed by a top official from Twitter, came as debate intensified over whether oversight of government spying programs grew too lax in the aftermath of the Sept. 11, 2001, terrorist attacks, when security concerns combined with soaring technological capabilities led to individuals being monitored on a vast new scale.

The Senate Intelligence Committee, whose chairman, Sen. Dianne Feinstein, has defended the surveillance efforts, asked the NSA on Tuesday to publicly explain programs that use telephone and Internet records "so that we can talk about them, because I think they're really helpful," she said.