Reliance Industries Chairman Mukesh Ambani has received a third threat email in four days, this time demanding Rs 400 crore. The email was received on Monday, following earlier emails seeking Rs 20 crore and Rs 200 crore on Friday and Saturday, respectively. The Mumbai police, including crime branch and cyber teams, are actively working to trace the sender. Last year, a man from Bihar was arrested for making death threats to Ambani and his family, including a threat to blow up the Sir H N Reliance Foundation Hospital in Mumbai.