A man claiming to be an associate of gangster Dawood Ibrahim dialled up Maharashtra Chief Minister's residence on September 5.
The call led to ringing of alarm bells in the administration and security was boosted at 'Matoshree', CM Uddhav Thackeray's personal residence in Mumbai.
Two calls were made around 10:30 pm and the caller claimed to be phoning from Dubai and asked to be connected with the CM.
Police are trying to locate the caller and identify him.