U.S. intelligence agencies hacked into the email servers of Chinese tech giant Huawei five years ago, around the time concerns were growing in Washington that the telecommunications equipment manufacturer was a threat to U.S. national security, German weekly Der Spiegel reported Saturday.

The National Security Agency began targeting Huawei in early 2009 and quickly succeeded in gaining access to the company’s client lists and email archive, Der Spiegel reported, citing secret U.S. intelligence documents leaked by former NSA contractor Edward Snowden.