Eleven people accused of spying for Russia were formally charged in a US indictment, more than a week after the FBI announced their arrests.
The indictment charged all the defendants with conspiring to act as secret agents and also charged nine of them with conspiracy to commit money laundering.
The indictment, a charging document that can be used during a trial or if the defendants enter a plea, contains far fewer details of the alleged crimes than were inside two criminal complaints filed last week.
The defendants must appear before a judge to enter pleas to the indictment.
Prosecutors released a copy of the indictment yesterday, the same day that federal judges in Boston and Alexandria, Virginia, signed orders directing that five defendants arrested in Massachusetts and Virginia be transferred to New York, where the charges originated.
The legal developments came amid reports that American officials were meeting with the Russian ambassador in Washington and a claim by the brother of a convicted spy in Russia that his brother has been told he will be swapped for Russians arrested in the US.
Janice Oh, a spokeswoman for US Attorney Preet Bharara, declined to comment on speculation about a spy swap.
The defendants were accused of living seemingly ordinary lives in America while they acted as unregistered agents for the Russian government, sending secret messages and carrying out orders they received from their Russian contacts.
All have remained in custody except for a man identified as Christopher R Metsos, who was ordered released on bail last week by a court in Cyprus and is now a fugitive.