KOLKATA: A lone ATM in the heart of south Kolkata became a tool for fraudsters to rob more than 50 people, most of them staying within a one-km zone around Golpark, of more than Rs 20 lakh in a span of 120 hours, presenting the city’s police force with a whodunnit that it has never been called upon to solve before.As news of the fraud broke on Tuesday afternoon, dozens of duped customers from homes ranging across Purna Das Road, Ballygunge Gardens and Kankulia Road descended on a bank branch ( Canara Bank ’s Golpark branch) and one police station (Gariahat), demanding payback from the bank and redress from cops.Bank officials admitted that the case was unprecedented in the city for its sheer scale (the number of people duped from a single ATM) and its audacity though the amount robbed might have been “only around Rs 20 lakh”. “I cannot recount any single ATM being used to rob so many people over such a length of time in Kolkata,” a former SBI official said. Several of the withdrawals were logged as having made at an ATM at Delhi’s Palika Bazar, around 1,500 km from the Kolkata ATM.Both bank and police officials agreed on the probable method used—skimming— which they described as “tried and tested”. “Fraudsters copy your card data from its magnetic strip, using a small device called a skimmer, and then use that data to clone your card and withdraw money from your account,” a bank official said.“Preliminary investigation shows that the ATM was severely compromised. It appears to be a case of skimming,” joint commissioner of police (crime) Praveen Tripathi said. Cops have formed a special investigation team, roping in officers from the anti-bank fraud cell and the cyber cell, to probe the spate of complaints. A team is likely to leave for Delhi shortly.The scope of the fraud, however, may widen yet. One of the victims has been traced to Burdwan, around 120 km from the Canara Bank ATM, and cops say they are waiting for more victims to turn up and lodge complaints.Till Tuesday evening, a total of 27 complaints were lodged at the Gariahat police station. Two other FIRs — for unrelated bank frauds — were registered at Tiljala and Beniapukur police stations, which cops said they would probe along with the ATM crime.A senior official from the Gol Park branch of Canara Bank lodged a complaint with the Gariahat police, suspecting that the ATM — located at the branch itself — might have been compromised. “We have taken the issue very seriously and are cooperating with the police probe,” a senior bank official said. “We will try to redress our customers’ grievances as soon as possible,” he added. Reserve Bank of India guidelines mandate that customers should get back their money in such cases.Most of the victims withdrew money from the ATM in July. Many of them had accounts at the same Gol Park branch but there were people with accounts in other banks but who used this particular ATM to withdraw money.Victims were taken completely unawares for two reasons: one, none of them made any purchase using their credit/debit card nor had they shared any OTP details recently; two, the messages informing them of the “withdrawals” came between 9 p.m. and 11 p.m. on weekends, making it impossible for them to contact the bank directly.IT firm executive and Purna Das Road resident Kaushik Bose received two back-to-back messages at 8.34 p.m. on Saturday, informing him of two withdrawals — each of Rs 10,000 — in Delhi. “This was from my HDFC Bank salary account. As I tried to digest what was happening, two more messages came two minutes later, informing me that I had lost Rs 20,000 more,” he said.Unrelated complaints came from other parts of Kolkata. Ajay Chowdhury lodged a complaint at Tiljala police station, saying he lost Rs 35,000 from his bank account; Wasif Ali lodged a complaint at Beniapukur police station, alleging he lost Rs 50,000. Claims of people having lost money surfaced from areas like Park Street, Bowbazar, College Street and Jadavpur but cops said they were yet to receive any formal complaint. “We are also probing these cases,” JCP Tripathi said.