Calcutta, March. 1 :    Calcutta, March. 1:  The Boeing-737 spares, worth Rs 4 crore, stolen towards 1998-end from the Indian Airlines engineering complex at Dum Dum airport, have still not been retrieved, officials said on Friday. The director of vigilance, Indian Airlines (IA), had even conducted a preliminary inquiry into the theft but three years have elapsed and the 'IA authorities are now trying to hush up the case', sources alleged. 'We are sure the authorities are trying to shield some senior officers,' they added. The store, on the airport premises, from which the parts were reportedly stolen, is heavily guarded. Senior IA officials record each transaction in the register. 'Yet, no one has an inkling how the Boeing spares were stolen,' said an official. Sources said some of the stolen spares have reuse value, since Boeing-737s are still flown. Ever since the Boeing company stopped manufacturing 747 spares, accessories of the plane are much in demand, the sources said. Around 15 to16 years ago, the sources recalled, aircraft spares were stolen from the premises and later recovered from a nearby pond. Some time ago, the hooter of the siren, at the main gate of the engineering complex, was stolen. 'Besides, modern cooking appliances worth lakhs, have been stolen from the canteen over the years and yet no action has been taken,' the sources added.