How to find out IPG whats app scam fraudsters which duped lakhs of rupees of their customers.

One of my friend invested amount in IPG rent app through what's app link forwarded by his friend. This app was running successfully from last 3 months and gained trust of people. They offered many attractive rents/ schemes with daily incomes and daily rewards luring customers to deposit more money for instant earning. Reaching different levels encouraged more people by which one can gain additional profit by adding more people. Few joined their family members, relatives and close friends who trusted them and started depositing money. But Saturday onwards that what's app chat group was not active, seen as only admin can forward message. People were unable to contact either through call or chat. Panic situations were created. Most of them didn't withdraw amount from IPG accounts to their personal account. Many people who invested amount recently got completely duped by this online fraud app. Now neither that IPG app is working nor any contact number is functioning. People were able to chat in group as well as personally to Group admin for any queries. But Saturday onwards nothing is active. Even the app page is closed completely. This fraud gang will definitely again start another what's app group and successfully dupe many more innocent people. Cybercrime was approached by my frnd , they mentioned that if the amount was invested at your own risk, then it is not possible to recover. They suggested to File an FIR. If timely action is not taken, this fraud gang will move free and take advantage of more chances to dupe many innocent people. People join this kind of app may be due to financial problems, to make instant money, trust, addiction to earn online money etc. Kindly suggest how to handle this kind of scam apps.