An attendant saw the warning scrawled in large letters proclaiming "CSI Atteck by ISIS 10/01/2015", and alerted the authorities.

Officials of the Mumbai International Airport Ltd. (MIAL) gave a guarded response, saying they had no information on who could have scrawled the message but police were probing the matter.

It was not immediately clear whether the threat could be real or merely a prankster's scribble, but the security agencies are not taking any chances.Police and the Central Industrial Security Force have tightened measures and are on the lookout for the person who could have penned the message.

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