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BERLIN (Reuters) - A German military helicopter that crashed while flying a peacekeeping mission in Mali began to break up while in flight, losing its rotor, according to a defense ministry report seen by Reuters.

Two crew members were killed when one of Germany’s four Tiger helicopters crashed in the West African nation’s desert north last month. At the time, German officials said there were no signs it was downed by an attack.

An in-air break-up could point to maintenance or manufacturing issues having contributed to the crash, although the report said it was too early to speculate about the causes of the crash.

“According to information available so far, once the vehicle had started to descend, parts of the aircraft broke off, including the main rotor blades,” the ministry report said, adding that the flight had proceeded normally until then.

The deployment of the Tiger helicopters to Mali earlier this year was controversial since the aircraft, made by Airbus, required extra maintenance given the high heat and other environmental conditions in the desert country but officials said at the time the four vehicles had been performing normally.

The report said the aircraft had been flying at 250 kilometers (155 miles) per hour at a height of 550 meters (1,800 feet) when it “suddenly sank its nose and entered a sharp dive.” The helicopter crashed 10 seconds later and burst into flame.

Germany agreed to deploy the four Tiger and four NH-90 transport helicopters to Mali earlier this year after the Dutch military said it could not continue the work.

But Germany’s increased support was heavily debated in parliament, and required a waiver from the German military allowing the helicopters to operate in higher temperatures.

German armed forces operate a fleet of 27 of the helicopters.