Bharat Petroleum [BPCL] — All gas cylinders received at home are 3 to 4 kg less in weight.

I have been checking gas cylinders from past 4 months and have found all gas cylinders received at home are 3 to 4 kg less in weight as shown on cylinder. All cylinders are sealed but weight is less.This seems to be a big scam .If you could do something please do so or I will escalate it to the PMO office.