India's cricket captain Mahendra Singh Dhoni [Images] has received a letter carrying a threat to harm his family if he does not pay up Rs 50 lakh while the police on Wednesday said they are taking "all precautionary measures" and that his security has been further tightened.

Police said that the letter was sent to Dhoni's family by a person claiming to be a member of the underworld don Dawood Ibrahim's [Images] gang but maintained "it is actually a letter that has originated locally from a colony which is very much inside Ranchi and not very far from where Dhoni lives."

• Dhoni strokes style, spirit and substance

Suspecting that the letter could be a job of "local criminals," Inspector General and Jharkhand police spokesman S N Pradhan said, "The perceived threat from the underworld gang is for the moment ruled out."

He, however, said that "we are taking all precautionary measures and I am sure it will be sort out quickly."

Ranchi Senior Superintendent of Police Sampat Meena said police were investigating the source of the letter and "we cannot say much about it at the moment."

• Dhoni with his body double

She was replying to questions on reports published in Hindi newspapers that Dhoni's father Paan Singh had received the letter on December 29 from a person named Taslim who claimed that he was a member of Dawood's gang.

Police said security has been tightened with personnel from Special Task Force guarding Dhoni's residence at Mecon Colony in Ranchi.

Pradhan said, "it appears to be an act of mischief by local criminals. In that colony there are two rival groups that tend to trap and expose each other. So we believe this is some kind of mischief going on but we would not like to underplay it."

He said Dhoni enjoyed security cover on par with high "Z" category and that "it has been upgraded." Extra police forces have been deployed in and around his house, he said, adding that "when he moves there is plenty of security."