'To Russia with love via Dublin'
Irish police Commissioner Fachtna Murphy has said detectives are investigating the possibly fraudulent use of six Irish passports.
One passport belonged to a volunteer with Irish charity 'To Russia With Love'.
It is believed to have been cloned and used by one of the 10 Russian spies deported from the US in July.
Commissioner Murphy told RTE that the gardai had been working "very closely" with US law enforcement agencies.
He added that the investigation had been underway for some time.
A statement from To Russia With Love said members of the charity were very distressed and had been co-operating fully with the Gardai.
"This is a unique incident and nothing like this has ever happened before," the statement said.
"We do not know where or when the passport became compromised, to the best of our knowledge our systems have never been tampered with in any way."
The charity has been working in Russia for more than 12 years helping Russian orphans across the Russian Federation.
The latest garda investigation follows another set up to investigate the forgery of Irish passports by Israeli agents.
That investigation found that eight forged Irish passports were used in connection with the killing of a senior Hamas figure in Dubai earlier this year.
It also found that an Israeli Government agency was likely to have been responsible for the production of the forged passports.