Three people died after a sightseeing plane crashed in northern France Saturday, following what is thought to have been an engine failure, the local prosecutor said.The four-seater Robin HR 100 had just taken off from an airfield when it crashed and caught fire near Wambrechies, near the city of Lille, said prosecutor Carole Etienne.Air accident investigators were at the scene, and at this stage, the thinking is that it was an engine failure, said Etienne.The three people on board, aged 29, 53 and 61, had been bound for Belgium, she added.