Tests for the presence of lethal radiation levels at NUI Maynooth and the Connolly Hospital in Blanchardstown in Dublin have shown negative results.
The tests were carried out after a former Russian Prime Minister who had visited the two locations took ill.
Earlier the Radiological Protection Institute confirmed that it was assisting the gardai and the Health Service Executive with their investigations into the mysterious illness suffered by Yegor Gaidar.
Meanwhile, a second man has tested positive in Britain for the radioactive toxin.
Italian academic Mario Scaramella met with Mr Litvinenko at a sushi restaurant in London the day he fell ill.
A post mortem on Mr Litvinenko's body took place in Britain today.
- Morning Ireland: Seamus Martin, former Irish Times correspondent in Moscow, explains what happened on the day Mr Gaidar became ill
- Morning Ireland: Journalist Conor Sweeney explains that former Russian Prime Minister Yegor Gaidar is being treated in a Moscow hospital amid rumours about the cause of his mystery illness
- Nine News: Conor Mark Kavanagh reports on the radioactivity test being carried out by the Radiological Protection Institute in Maynooth
- Six One News: Conor Mark Kavanagh reports that RTÉ News has learned that radioactivity tests are being carried out at NUI Maynooth and Connolly Hospital after a former Russian premier fell ill

