"A case on the suspicion of negligent homicide has been opened against three people who are said to have carried out" work on the Airbus helicopter, prosecutors in the southern town of Kempten said.

Earlier, European aircraft maker Airbus said a probe had found that "an improper setting of the helicopter controls was identified by the investigation as one of the factors in the chain of events which have led to this catastrophic outcome".

Two German UN peacekeepers were killed in July 2017 when their Tiger helicopter crashed as they were monitoring fighting in northern Mali.

UN sources in the area quickly ruled out it was shot down, and the German army has since been looking into the reasons for the crash.

German prosecutors said a report from the German Military Aviation Authority has found that "works on the helicopter had been incorrectly carried out during the adjustment of the main rotor control system."

"The faulty adjustment of the rotors led to a situation in which the chopper could no longer be controlled by the crew during a routine flight, leading to the crash."

The United Nations operation in Mali, launched in 2013, is considered the UN's most dangerous peacekeeping mission, with dozens of its staff killed over the past four years.

Germany had reinforced its presence in Mali in 2017, deploying several Tiger combat helicopters and raising the number of Germans serving in MINUSMA to 639 as of June, the army's largest presence overseas.

Northern Mali is the site of frequent clashes between rival armed groups, as well as a haven for jihadist activity.

hmn/fz/nla

AIRBUS GROUP