A judge in Chile has ordered the arrest of 13 former army officers for their alleged role in executing political opponents of Gen Augusto Pinochet.
The fate of many victims of the Pinochet regime remains unknown
At least 75 people were executed in the so-called Caravan of Death operation, which took place soon after the 1973 coup in which Gen Pinochet took power.
The 13 indicted officers served in regiments visited by the "Caravan" and allegedly took part in the killings.
Correspondents say the case has become a symbol of Pinochet-era repression.
It dates back to October 1973, when a self-styled military "delegation" toured Chile in a helicopter to summarily execute political opponents of Gen Pinochet's September coup.
Many of the victims had voluntarily turned themselves in to the military authorities.
The tour was one of the most notorious cases of human rights violations committed during Gen Pinochet's 17-year military government.
A dozen other army officials are already facing trial for their alleged role in the operation.
Among the newly-indicted military personnel is Carlos Minoletti Arriagada, the former head of an engineers' regiment now living in the US.
Prosecutors and the families of the victims feared the case would never come to court, the BBC's South America correspondent Daniel Schweimler says.
Charges against Gen Pinochet over the Caravan of Death were dropped
But they have been angered by Judge Victor Montiglio's decision to change the charges faced from kidnapping to murder.
The change means those charged could, in theory, be covered by a 1978 amnesty issued by Gen Pinochet's regime.
The original kidnapping charges were based on the grounds that bodies of many victims had never been found - thus making it a "crime still in progress" not covered by the amnesty.
Gen Pinochet was himself indicted on charges relating to the Caravan of Death in 2001, but the case against him was dropped a year later on health grounds. He denied involvement.
The 90-year-old is still being investigated for tax evasion and corruption.