The arrests earlier this week of 11 people suspected of being Russian agents was the result of almost 10 years of FBI monitoring, The Washington Post reported Saturday.
Court documents and an interview with a senior U.S. official reveal that federal investigators had already searched some of the suspects homes, installed surveillance equipment and monitored their communications and meetings by mid-2006, the Post said.
In June 2006, for example, the FBI tracked suspects Michael Zottoli and Patricia Mills traveling to Wurtsboro, N.Y., where Zottoli dug up a package of money that had been buried there two years earlier by another conspirator, the AP reported.
Despite the evidence collected, the FBI waited until last Sunday to arrest those involved because it felt that valuable counterintelligence information could be gained from allowing the alleged spies to continue operating, the Post said.
This counterintelligence information included decoded messages and names of Russian couriers, spy handlers and American recruits, as well as Russian espionage tactics, the Post reported.