Adulteration of fuel at petrol bunks in the city is on the rise. At least 1,075 cases have been registered this year against various oil companies as against 931 cases last year. According to legal metrology department, at least 299 cases have been booked against HPCL, 531 against IOC, 188 against BPCL and 17 against Reliance in 2007-08. Receipts with oil companies showed a fall in total revenues from sales of diesel and petrol despite the increase in sale of vehicles, the officials said. They attributed the discrepancy to adulteration of fuel at petrol bunks. "The violations of standards of weights and measures even in retail outlets is probably due to lack of vigilance within the establishments,' said the legal metrology director, Ms Tejdeep Kaur Menon. The department was apparently told by approved testing labs that seized samples were within Bureau of Indian Standards specifications. Department officials said that, in reality, large-scale adulteration of fuel is taking place at many petrol bunks. The AP Forensic Science Laboratory, that also conducts tests on fuel for adulteration, feels the range permitted in BIS specifications is too large. The legal metrology department is seeking approval from BIS for gas chromatography tests which could detect minute levels of adulteration. Meanwhile, the anti-fraud wing of the city police has found that cases of credit card skimming at petrol pumps are also increasing. A senior police official said, "It is dangerous to hand over credit or debit cards to petrol pump staff. Double swiping and credit card cloning has become commonplace.'