The state news agency IRNA had earlier described the attackers as "bandits," and said authorities were investigating whether the attackers were drug smugglers or an armed opposition group.
An Iran official meanwhile said that authorities would probe claims by the daughter of detained opposition leader Mir Hossein Mousavi that she was bitten and hit by a female guard during an argument that broke out after she was allowed to visit her parents.
IRNA quoted an unnamed security official as saying that the Intelligence Ministry, which supervises the detentions of the elder Mousavi and his wife, will investigate any failures or fault by the guard. However, the official said Mousavi's daughter was at fault in the incident, claiming that she insulted and attacked the guard.
The opposition Kaleme website on Friday recounted the allegations by Nargess Mousavi: that she was abused by the guard, who demanded that she and her sister consent to a strip search after visiting her parents, who have been under house arrest since early 2011.
Nargess Mousavi claims the guard struck her in the head and bit her on the wrist after she refused to be searched.
The elder Mousavis and fellow opposition figure Mahdi Karroubi were placed under house arrest after leading protests in 2009 over the disputed re-election of then-President Mahmoud Ahmadinejad.