A man believed to be a German intelligence operative has been arrested on suspicion of being a double agent for the US.
A spokesman for Chancellor Angela Merkel said she had been informed of the arrest but refused to give any further details.
"The Chancellor was... informed of this case," Merkel spokesman Steffen Seibert told reporters in Berlin.
Earlier this week, Federal prosecutors announced they had arrested a 31-year-old who they said had been spying for a foreign power, but didn't disclose the suspect's name or for whom he was allegedly spying.
Later, Der Spiegel magazine and daily newspaper Sueddeutsche Zeitung reported that the man was an employee of the Bundesnachrichtendienst or BND, Germany's equivalent of the American CIA.
Citing unidentified sources, the reports said that he had been paid by the US to provide information about a German parliamentary committee set up to investigate what kind of spying activites were being carried out by the US and other intelligence agencies in Germany.
The committee was formed after allegations by NSA whistleblower Edward Snowden that the US government tapped Chancellor Angela Merkel's phone.
Revelations of the NSA's scooping activities in Germany were described as "grave" by Merkel and, at the time, soured Berlin's relationship with Washington.
In January, US President Barack Obama moved to improve relations by halting NSA spying on allied world leaders and pulling back the NSA surveillance programme.
Merkel's spokesman said the Chancellor made a phone call to Obama after the alleged double agent was arrested but the conversation focused on "foreign policy matters".