FBI Director Robert Mueller has defended the Obama administration’s mass collection of domestic phone records, saying such practices are legal and done in the interests of national security. Speaking before the House Intelligence Committee Thursday, Mueller also confirmed the administration has launched a criminal investigation into Edward Snowden, the whistleblower who leaked the secret documents about NSA spying.

Robert Mueller: “As to the individual who has admitted making these disclosures, he is the subject of an ongoing criminal investigation. These disclosures have caused significant harm to our nation and to our safety. We are taking all necessary steps to hold the person responsible for these disclosures. As this matter is actively under investigation, we cannot comment publicly on the details of the investigation.”

Edward Snowden is believed to be hiding out in Hong Kong.