Special police units in Germany have arrested two suspected spies who are believed to have been active for 20 years. The married couple are said to have worked for the Russian Foreign Intelligence Service. According to the reports, the two entered Germany via Mexico with false papers in 1990 and spent years sending coded messages to Russian Intelligence using a shortwave receiver. Russian officials greeted the reports with silence, but one foreign intelligence agent said the couple was probably a part of a retired network of spies Moscow has kept in Europe since Soviet times. "What we are talking about is not espionage activity," the unnamed Russian intelligence agent told the Izvestia daily. He added that such retirees were often used as "mailboxes" by Moscow for relaying sensitive information in special cases. "They are already retired, they have families -- and nevertheless, now and then, they transmit and receive information. Sort of like a 'mailbox' -- we do not leave them behind," the Russian agent said.