What is HPZ Token scam that has put payment gateways in ED spotlight?

The HPZ Token scam, in which eight payment gateways, including Paytm, PayU, and Razorpay, have been under the Enforcement Directorate’s (ED) scanner as per a report by The Times of India, is said to have started with the launch of the ‘HPZ Token’ mobile app. The app-based token promised investors humongous gains by investing in mining machines for Bitcoin and other cryptocurrencies.