FBI agents arrested 10 people on charges that they spent years in the United States as spies for Russia, taking on fake identities and trying to ferret out intelligence about U.S. policy and secrets by making connections to think tanks and government officials, the Justice Department said Monday.

The arrests Sunday capped an almost surreal investigation that extended to the Clinton administration and involved video surveillance, hidden microphones and surreptitious FBI searches of homes along the East Coast. It climaxed Saturday with a fake “drop” in a park in Arlington County, when one of the suspects left $5,000 in an envelope inside a folded newspaper, which was recovered by the FBI…

Whether it succeeded was unclear Monday. Federal law enforcement officials portrayed their operation as a spectacular counterintelligence success that uncovered a group of spies capable of doing great damage to U.S. national security. “I can’t remember a case where we’ve been able to arrest 10 intelligence officers from a foreign country in one fell swoop,” one official said. “This network in the United States has now been completely compromised.”

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Jessie Gugig, 15, said she could not believe the charges, especially against Mrs. Murphy, who was an accomplished gardener.

“They couldn’t have been spies,” Ms. Gugig said. “Look what she did with the hydrangeas.”

There were also hints that Russian spy bosses feared their agents, ordered to go native in prosperous America, might be losing track of their official purpose. Agents in Boston submitted an expense report with such vague items as “trip to meeting” for $1,125 and “education,” $3,600. In Montclair, when the Murphys wanted to buy a house under their names, “Moscow Center,” or “C.,” the S.V.R. headquarters, objected.

“We are under an impression that C. views our ownership of the house as a deviation from the original purpose of our mission here,” the New Jersey couple wrote in a coded message. “From our perspective purchase of the house was solely a natural progression of our prolonged stay here. It was a convenient way to solving the housing issue, plus ‘to do as the Romans do’ in a society that values home ownership.”