Mumbai Police said it is too early to say if the letter is fake.
Mumbai Police Commissioner Sanjay Pandey on Monday said they have taken the threat letter received by Bollywood actor Salman Khan "seriously", and all angles of the case will be probed.
Earlier in the day, a police team visited Salman Khan's residence in suburban Bandra and increased security around the premises, a day after the actor and his father and screenplay writer Salim Khan received an anonymous letter threatening to kill them.
Talking to reporters, Mr Pandey said, "As the matter is serious, so we have also taken this issue seriously. Our officials are actively investigating the case. No one has been detained till now.
"It's too early to say if the letter is fake, and also we can't say anything about the (involvement of) Lawrence Bishnoi gang. But whatever content is there in the letter, we are taking it seriously and conducting probe," the commissioner added.
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