The FBI is no longer actively involved in the investigation into the murder of the Lurgan solicitor, Ms Rosemary Nelson, an FBI spokesman has confirmed.
The bureau was available on a "stand-by" basis to help the investigation, and it would be up to the RUC, which originally asked for FBI help, to decide what further help the US bureau could give, he said.
He emphasised that in cases where the FBI helped foreign police forces at their request, the US agents did not have "investigative authority".
Diplomatic sources here said that in the Nelson investigation, the FBI would still be available to give forensic help if required.
The FBI spokesman said that in the case where a suspect was in the US, the bureau would also get involved.
Following the murder of Ms Nelson on March 15th, the RUC Chief Constable, Sir Ronnie Flanagan, announced that he had asked for FBI assistance as well as asking senior British police officers to help in the investigation.
He said the FBI involvement would "give the investigation an international dimension and an independence that is unprecedented in any investigation we have had before".
The role of the FBI in the Nelson investigation was later queried by Republican Congressman Chris Smith in the US Congressional hearing on the reform of the RUC on April 22nd.
Mr Smith was reported by The Irish Times in that hearing as saying that the FBI officers assisting the RUC had "no operational control" and could not issue search warrants.
Mr Smith claimed that they were "just observers and have now been pulled out".
An internal memo from Mr Smith's office is cited in the latest issue of the Irish Echo as saying that the FBI had two agents in Northern Ireland for less than three weeks.
They were accompanied by Mr John Guido, the legal attache at the FBI office in London.
The FBI had pulled out of the on-the-ground investigation by April 16th, according to the internal memo, said to be based on contacts between Mr Smith's office and the FBI's Congressional liaison officer.
The director of the FBI, Mr Louis Freeh, refused to answer questions about the bureau's role in the Nelson investigation when he was in Dublin earlier this month at an international police conference.
Mr Guido publicly expressed confidence in the professionalism of the RUC while he was in Belfast.
The RUC said yesterday that media comment on the investigation was a matter for Mr Colin Port, the Deputy Chief Constable of Norfolk, who is in charge of the Nelson murder inquiry.
Mr Port could not be contacted for comment last night.