US 'may never know extent of information Edward Snowden leaked: Report

U.S. officials have concluded they may never know the full extent of information leaked by the National Security Agency whistleblower Edward Snowden.

According to a report published by the New York Times, senior government officials said investigators are unsure of the scope of information Snowden collected.

The officials added that the Hawaii data facility Snowden worked at did not have employee-monitoring software with which other NSA facilities were equipped, the Guardian reports.

Such software is meant to detect unusual behavior among NSA's approximately 35,000 employees.

The leader of the presidential advisory committee, Rick Ledgett, believes Snowden has access to documents that have not yet been disclosed, the report added.