Here are the latest developments in this story:
Bangalore police said Mehdi got interested in the developments in the middle-east - Turkey, Syria, Lebanon, Israel, Gaza strip, Egypt & Libya - since 2003. He used to work during the day and surfed internet on a 60 GB monthly plan late into nights.
During his initial questioning, Mehdi said Indian Muslims were incapable of Jehad, so he was concentrating on Muslims living aboard, said Bangalore police. Most of his 17,000 followers on Twitter were English-speakers from Europe.
While most of his tweets have been deleted and the account has been closed, police say they have found no anti-India activity or tweets so far. There is nothing to suggest that he had wanted any terror attack in India.
Although Mehdi was in contact with English-speaking IS men on Twitter, he was careful to hide his true identity from them.
So far, he has not recruited anyone or facilitated any recruitment and was more into propaganda, authorities say. He was mainly translating Arabic tweets into English. He also collected data and videos from cyberspace and then posted them on the web.
Mehdi has been also been active only in the virtual world and has never travelled outside India. The police added there was no evidence to show any funding came from IS to Mehdi.
The UK-based Channel 4 News, which reported on the issue on Thursday, said, "His tweets were seen two million times each month, making him perhaps the most influential Islamic State Twitter account."
An electrical engineer from Kolkata, Mehdi had moved to Bangalore in 2011. He had been employed with the multinational corporation as a marketing executive since 2012 at an annual salary of Rs 5.3 lakh.
Mehdi has been accused of waging war against the nation, waging war against a friendly nation and under sections of the IT Act. Police say he has no previous criminal record. His cellphone and laptop were seized during his arrest.
Mehdi has two sisters and his father is a retired employee of the West Bengal State Electricity Board. "My son can never do this, I will never believe this," his father said.