The parcel are delayed because of inland transportation within country and Customs clearance procedures.
It depends on what do you import and from where do you import.For example, gold and jewellary items require valuation by the jewellary Expert of the Customs department.Similarily drugs and medicine are required clearance from The Assistant Drugs Controller.If you are importing Insecticide and pesticide then you have to obtain clearance as per Insecticide Act.The same procedure is followed whether you receive goods through post, Air cargo ,ICD,and Seaport.
The postal department does not assign any local number if the parcel is not detained by the Customs department.
But ,if it is detained for want of information, then you receive intimation from Postal department with local number and also from the Customs department.
you can enquire status of parcel with this local reference number at Customer care centre of Foreign post Office..