Eight Iranian inmates were killed in a fire that raged through Tehran’s Evin prison, the judiciary said Monday, doubling the official toll from the blaze that further stoked tensions one month into protests sparked by the death of a woman in Police Custody, Mahsa Amini.

Authorities in the Islamic republic have blamed the fire late Saturday on riots and clashes among prisoners, but human rights groups said they doubted the official version of events and also feared the real toll could be even higher.

The judiciary said Monday that four Evin prison inmates injured in the fire had died in hospital, after reporting the previous day an initial toll of four dead from smoke inhalation.

Gunshots and explosions were heard during the dramatic blaze from inside the complex, according to social media footage.

Iranian authorities have accused thugs of torching a prison clothing depot and reported clashes between prisoners, and then between inmates and guards who intervened to put an end to the violence.

Hundreds of the protesters arrested in recent weeks have been sent to Evin, infamous for the ill-treatment of political prisoners, which also holds foreign detainees and thousands jailed on criminal charges.