The Obama administration has launched an internal review of the potential damage to national security from leaks about US surveillance efforts, as a group of senators and technology companies are pushing the government to be more open about the top-secret programmes.

Google and others seek loosening of secrecy on requests

A senior US intelligence official said the review will be separate from a Justice Department criminal investigation into Edward Snowden’s disclosures about the National Security Agency’s broad monitoring of phone call and internet data from big companies such as Google Inc and Facebook Inc .

The review is expected to evaluate whether the leaks have compromised sources or surveillance methods, and would likely look for chatter among intelligence targets to see if the leaks have prompted them to change tactics.

Reporters staked out hotels in Hong Kong in hopes of spotting Snowden, an NSA contractor who went public in a video released on Sunday by Britain’s Guardian newspaper but then dropped from sight in the former British colony and has yet to resurface.

General Keith Alexander, head of the NSA and US Cyber Command, told the Senate Intelligence Committee in a closed-door briefing that he did not know where Snowden was, said Senator Saxby Chambliss of Georgia, the top Republican on the panel.

Booz Allen Hamilton, the company that most recently employed Snowden, said it had terminated Snowden’s employment on Monday for violations of its code of ethics and policies. It said he had been an employee for less than three months at an annual salary rate of $122,000 (€91,500).

The revelations from Snowden have launched a sharp debate about the tradeoffs between privacy rights and national security in the US and whether the surveillance measures have been given sufficient scrutiny and oversight.

Members of Congress promised an extensive public discussion and more legislative efforts to tighten the laws on US govern-ment surveillance.

“We’ll have a lot of hearings on this,” said Senator Barbara Mikulski, a Maryland Democrat. She said there were questions about how Snowden, a high-school dropout, gained a top-secret clearance and access to high-level government secrets.

A bipartisan group of senators introduced a Bill designed to end the secret supervision of the programmes by the Foreign Intelligence Surveillance Court by requiring declassification of significant court rulings.

“Americans deserve to know how much information about their private communications the government believes it’s allowed to take under the law,” said Senator Jeff Merkley, an Oregon Democrat and chief co-sponsor of the Bill.

Big technology companies have issued a series of pleas for the government to lift the veil on national security requests to the private sector. Google sent a letter to US authorities asking that secrecy restrictions be loosened so the company could publish the number and scope of surveillance court requests.