Authorities in Dubai yesterday identified 15 new suspects in the killing, bringing the total number of people allegedly involved in the death to 26.
Of the new suspects listed, six are said to have carried British passports, three Irish documents and three French.
Numerous media reports named the suspects travelling on false Irish passports as Ivy Brinton, Anna Shauna Clasby and Chester Halvey.
A spokesperson for the Department of Foreign Affairs yesterday said its information was that, of 26 suspects named in connection to the killing, it could confirm that six had used Irish passport details.
Dubai police also released passport photos and CCTV footage of the new suspects, and claimed two of them had left Dubai by boat bound for Iran.
Credit card details of some of the suspects involved in the assassination were also issued yesterday. Many were issued by the same bank in the US.
Hamas commander Mahmoud al-Mabhouh was killed last month in his hotel room in Dubai. Police in the United Arab Emirates have said it is 99% sure that Israeli intelligence agency Mossad was behind the killing.
To date, Israel has refused to confirm or deny its involvement in the incident, which has caused serious diplomatic strains between Israel and the European Union.
Fine Gael foreign affairs spokesman Billy Timmins yesterday called on Foreign Affairs Minister Micheál Martin to use all the resources of the state to get answers as to how such a serious security breach could occur.
“The minister must avail of all the security and diplomatic resources at his disposal to establish how bona fide Irish passport numbers fell into the hands of people accused of assassinating a Hamas leader.
“In doing so, the minister should also work closely with our partners in Europe to get to the truth of the matter.
“It is entirely possible that the Irish citizens who were legally assigned these passport numbers could have travelled overseas at the time of this incident and found themselves under arrest at a foreign airport through no fault of their own,” he said.
Earlier this week, it was confirmed that a vacant property in Dublin was given as an address by one of the suspects involved in the killing.
The property is owned by James Reynolds, brother of former taoiseach Albert Reynolds, and father of music promoter John Reynolds.
The address was given in a hotel in Dubai as the home address of a suspect in the killing, who was travelling under the name Kevin Daveron.
The Reynolds family have expressed their shock at the revelation and said they knew nothing about what had happened.