BERLIN — German authorities are investigating a second spy case reportedly involving the United States, a week after the arrest of a German intelligence employee cast a new shadow over relations between the two countries.

Federal prosecutors said Wednesday that police raided properties in the Berlin area on “initial suspicion of activity for an intelligence agency.” They did not elaborate or specify what intelligence agency was involved, but said they had not made an arrest.

“We have investigations in two cases of suspected espionage, a very serious suspicion,” government spokesman Steffen Seibert later told reporters in Berlin. He declined to provide further details, citing the ongoing investigations.

The daily Sueddeutsche Zeitung reported, without naming sources, that the man being investigated worked at Germany’s Defense Ministry and is suspected of spying for the U.S. News website Spiegel Online reported, also without naming sources, that the man worked in a department dealing with international security policy and had aroused the suspicion of Germany’s military counter-intelligence agency because of his close contacts to alleged U.S. spies.

Defense Ministry spokesman Lt. Col. Uwe Roth declined to confirm the reports, but said the case fell “into the ministry’s area of responsibility” and that Defense Minister Ursula von der Leyen had been informed.

State Department officials traveling with U.S. Secretary of State John Kerry in Beijing had no immediate comment. The White House also declined to comment, although press secretary Josh Earnest reiterated that the U.S. appreciates its “important partnership” with German national security officials.