No radiation has been found at Irish sites visited by Russian politician Yegor Gaidar, who fell mysteriously ill last week.
The Radiological Protection Institute conducted tests at the National University of Ireland, Maynooth, where Mr Gaidar collapsed last week, and at Connolly Hospital in Dublin, which treated him.
The test were spurred by ex-KGB spy Alexander Litvinenko's poisoning in London.
The HSE had described the tests as a purely precautionary measure after Mr Litvinenko's death from radiation poisoning, where fears have been raised of wider contamination.
Mr Gaidar, 50, who is now an influential academic, had been in Ireland to promote his new book but was later moved to a Moscow hospital.
Doctors are to carry out further tests on Mario Scaramella, one of the last people who saw Mr Litvinenko before he fell ill.
Both men were exposed to the Polonium-210, the radioactive substance which caused Mr Litvinenko's death.
It was also revealed last night that Mr Litvinenko's widow, Marina, had also come into contact with a radiation.
However, both she and Mr Scaramella are not thought to be in any danger.
Over the past week, traces of radiation have been detected at around 12 sites, including three British Airways planes that had flown between the UK and Russia.
The Chief Executive of the British Health Protection Agency, Pat Troupe, said people should not be worried about the traces of radiation being found at other locations.
