Canada has dismissed the latest explanation from Iran's judiciary concerning the death last year of Canadian journalist Zahra Kazemi.
Kazemi died after falling into a coma
The claim that Kazemi's death in custody was an accident had "no credibility", the foreign affairs ministry said.
The Iranian-born journalist was arrested after taking photos outside a Tehran jail.
An intelligence officer was acquitted of her murder last Saturday.
"Justice demands that a new inquiry be conducted, and
conducted in a credible fashion," ministry spokesman Reynald Doiron was quoted by the AP news agency as saying.
Kazemi died in hospital in the capital on 10 July after falling into a coma, having received head injuries during more than three days of interrogation.
The judiciary cleared suspect Mohammad Reza Aghdam Ahmadi, an intelligence ministry agent, of her killing "due to lack of sufficient evidence".
A statement from the Iranian judiciary said that as the "sole defendant" in the case had been acquitted, there remained only one option to explain the death.
"This is that the incident leading to the death of the late Kazemi was because of a drop in her blood pressure caused by her hunger strike, thus making her fall from a standing position and get hurt," the statement said.
Both Kazemi's family and reformists in Iran have said the trial was part of a cover-up to protect a high ranking official in the conservative-controlled judiciary.
The BBC's Jim Muir in Tehran says an official has been widely named in the Iranian press and political circles as the man who struck the fatal blow or blows which killed Ms Kazemi, but the courts have so far refused to follow it up.
The case has caused a deep rift within Iranian political circles and outraged human rights organisations.
Reformist President Mohammad Khatami had also said he believed Mr Ahmadi was innocent and called on the judiciary to identify "the real guilty person".
The case soured relations between Iran and Canada and Ottawa recalled its ambassador in protest.
On Tuesday, Canada said it would ask the European Union and the United Nations to put pressure on Iran to resolve the case.