Three men remain in custody, and the prosecution has got until Tuesday to decide whether to charge them or not.
The arrests were made last Tuesday, on suspicion of plotting to assassinate Lars Vilks, who two and a half years ago drew the Prophet Mohammed with the body of a dog.
The drawing outraged many in the Muslim world and led to a 100 thousand dollar bounty being put on Vilks head by a leader of a group with links to al-Qaeda in Iraq.
On Friday, Wall Street Journal reported that one of the seven originally arrested in Ireland is an American woman. She is identified by the paper as a 31-year-old medical assistant from Colorado. A police source told AFP on Thursday that - apart from an American national - the group consists of three Algerians, a Libyan, a Palestinian, a Croatian national. It is not clear who of these were among those three released on Friday.
Earlier this week, another American woman, Colleen LaRose, alias "JihadJane", was indicted, accused plotting to kill a Swedish citizen and travelling to Europe for this purpose.
The US Justice Department has declined to say if LaRose was connected to the alleged plot to kill Vilks, but Irish police has confirmed that there were links between her and the seven arrested in Ireland.