Dhoni met Police officials on Wednesday, Dec 31 and handed over the letters and discussed about the family security. He later left Ranchi on Thursday, Jan 1 amid tight security.
Following Dhoni's complaint, Jharkhand police arrested three people, Ranjit, Sadiq and Parvez on Thursday, Jan 1. The three have been interrogated and Taslim's family members have been questioned to know his whereabouts.
"We are investigating three angles. First, was it really Taslim who wrote the letter, second, could it be the handiwork of any rival gang, and third, is it someone playing a prank," a police official said.
Ranchi police are also seeking help of the Crime Investigation Department (CID) in the investigations.
According to police, Taslim was a close associate of Surendra Bengali, a dreaded don of Ranchi, who is presently serving a life term in Hazaribagh central jail. Taslim left Ranchi in early 1990s and is said to have joined Dawood's gang.
OneIndia News (With inputs from Agencies)