The Swiss federal prosecutor has turned down a request to re-examine the facts behind the worst ever terrorist attack in Switzerland. In 1970, a Swissair plane exploded in mid-flight, killing all 47 passengers and crew on board.

Earlier investigations had concluded that a Palestinian terrorist group was behind the attack, but no individuals were ever brought to justice. The case was officially closed in 2000.

But a private citizen asked for the probe to be re-opened after FBI documents found their way into the media, pointing the finger at two unknown people from the then West Germany. However, on Thursday the Swiss prosecutor said the file would remain closed as the new evidence was not strong enough and because too much time had elapsed since the crime was committed.

Initial investigations into the bombing were closed in 1985, were re-opened ten years later and finally discontinued in 2000. That probe concluded that terrorists had meant to bomb an Israeli El Al flight, but the device had ended up in the Swissair plane because of a change to flight timetables.

The explosion brought the plane down close to the northern Swiss village of Würenlingen, near to the border with Germany.

In a later twist, a Swiss journalist in 2016 reported a suspected secret deal between Switzerland and the Palestinian Liberation Organization (PLO) in 1970 after the terrorist attack. The report alleged that an agreement was made to avert further attacks in Switzerland, although these claims and suspicions of a cover-up were never proven. 

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