Iran's environment chief said Tuesday that a government committee had concluded there was no evidence against wildlife activists rounded up on spying charges in recent months.
Isa Kalantari, head of the government's department of environment, told state news agency IRNA that the conclusion had been reached by a special four-man committee, including the ministers of justice, interior and intelligence, and the president's legal deputy.
"This four-member group has come to the conclusion that these detained individuals are in custody without having done anything and naturally they must be freed soon," Kalantari said.
Iran has multiple, overlapping intelligence agencies -- the most prominent are linked to the government, judiciary and Revolutionary Guards -- that often act independently of each other, so the committee's assessment may have no effect.
The government's intelligence ministry has previously stated there was no evidence against the arrested environmentalists.
"There is no document indicating the truth of the accusations levelled against these detained individuals," Kalantari said.
Little detail has been given about the detentions, which began with the arrest of eight members of the Persian Wildlife Heritage Organisation in January.
But the cases drew international attention after the renowned head of the organisation, 63-year-old Kavous Seyed Emami, allegedly committed suicide in prison a fortnight after his arrest.
Kalantari's deputy at the department of environment, Kaveh Madani, was also forced to flee the country last month after pressure from hardliners about his private life.
There have been reports of several more environmentalists arrested in the south of the country, although only three have been officially confirmed -- members of the Association for the Protection of Nature in Lavardin.
Iran faces severe environmental challenges, particularly linked to a prolonged drought and extreme air pollution.