Former NSA contractor Edward Snowden gained access to some classified documents at the NSA by persuading other agency colleagues to share their login credentials with him, according to an exclusive Reuters report.

Former U.S. National Security Agency contractor Edward Snowden used login credentials and passwords provided unwittingly by colleagues at a spy base in Hawaii to access some of the classified material he leaked to the media, sources said.

A handful of agency employees who gave their login details to Snowden were identified, questioned and removed from their assignments, said a source close to several U.S. government investigations into the damage caused by the leaks.

Snowden may have persuaded between 20 and 25 fellow workers at the NSA regional operations center in Hawaii to give him their logins and passwords by telling them they were needed for him to do his job as a computer systems administrator, a second source said.

Last month, Reuters also reported the NSA failed to install the most up-to-date anti-leak software at the Hawaii facility long before Snowden had been employed there as a contractor.  The software, which had been installed at other US government facilities, is designed to detect unauthorized access attempts.

Well before Snowden joined Booz Allen Hamilton last spring and was assigned to the NSA site as a systems administrator, other U.S. government facilities had begun to install software designed to spot attempts by unauthorized people to access or download data.

The purpose of the software, which in the NSA’s case is made by a division of Raytheon Co, is to block so-called “insider threats” – a response to an order by President Barack Obama to tighten up access controls for classified information in the wake of the leak of hundreds of thousands of Pentagon and State Department documents by an Army private to WikiLeaks website in 2010.

The Reuters report indicated that the Hawaii facility had not yet installed the software because “it had insufficient bandwidth to comfortably install it and ensure its effective operation,” according to a US official with whom the outlet spoke.

Snowden had only worked at the facility for about a month when he downloaded tens of thousands of confidential NSA documents.  In June, Snowden told a Hong Kong news outlet that he sought the position specifically to gather evidence on NSA surveillance.

Snowden’s disclosures have since sparked a series of congressional hearings on NSA surveillance programs.