Two city-based professionals,who were working from home and using the Zoom video calling app, allegedly received ransomware threats, demanding payments in bitcoins, police said on Wednesday.The hackers demanded ransom to release the data which were encrypted from their computers, a senior officer of the Kolkata Police said.Both of them were using Zoom. They alleged of receiving emails from the hackers demanding payment in bitcoins. In the mail a specific link was also shared to purchase bitcoins, an official of the cyber-crime department said.It has been alleged that the hackers have also threatened that non-compliance to their demands would lead to a permanent loss of the data, the officer said.According to one of the complainants, the hackers have demanded USD 1,000 in bitcoin to decrypt the files, police said.Besides the cyber-crime department, the Special Task Force (STF) has also started an investigation into the matter, they said.These hackers target vulnerable computer systems and then attack them using ransomware to steal sensitive files. We are checking how the Zoom app was used in this crime. We are also checking the link sent in the mail to find out more about the matter, the officer said.There have been security concerns over the Zoom platform with the Centre stating that it is not safe and not to be used by government officials.The warning, earlier issued by Computer Emergency Response Team (Cert-In), was reiterated by the Cyber Coordination Centre (CyCord) of the Home Ministry in an advisory on April 16.Zoom became a popular application for executives working from home during the nationwide lockdown, announced by the central government to contain the spread of the coronavirus.