Former Indian cricket team captain Sourav Ganguly and his wife Dona Ganguly have allegedly received several threatening letters in recent months, including one that warned of killing the couple, Kolkata Police said on Tuesday.Former skipper Sourav Ganguly. (PTI)The matter came to light when the former skipper’s secretary approached Thakurpukur police station in south Kolkata to register a complaint. The complaint said the sender was identified as Arun and the letters were sent from Belghoria in North 24 Parganas district.The letters with hate remarks had allegedly been arriving in the former BCCI president's name for around six months, but were initially not taken seriously. On Monday, his office received two letters, containing explicit threats to kill him and his wife and harm people close to him, according to the complaint. “Initially we didn’t pay much attention to these letters, assuming that they were merely the work of someone who disliked Ganguly and was sending letters expressing his or her personal resentment,” the complaint said. The police said they are examining the contents of the letters and trying to confirm the identity and motive of the sender."We are taking the complaint seriously and have begun an investigation. We are examining the letters, their source and the courier trail to identify the person responsible," a police officer said on condition of anonymity. The police, the officer added, have begun examining the movement of the SIM card allegedly used by the sender and have contacted the courier agency concerned to gather details of the consignments. "We have spoken to the people from the courier service and tracked down one mobile number. We are trying to spot it," the officer said. The Kolkata Police are also ascertaining whether all the letters were sent by the same person, the officer added. There was no immediate comment from Sourav and his wife at the time of filing this report.