After receiving a tip-off from the US consul-general in Kolkata, the country's Western Naval Command issued a terror alert in early May for cities like Mumbai, Bangalore and Hyderabad and asked the local police and intelligence personnel to ensure strict vigilance.
The probable date for the attack, July 21, was mentioned in a communication from a little-known organization, al Jihad, to blow up important installations and railway stations.
The Al Jihad letterhead said that it would carry out destruction in Mumbai, Bangalore and Hyderabad in July.
The letter also threatened American consulates in Kolkata and Mumbai, saying that US citizens are its target.
The letter was handed over to Mumbai police and the Anti-Terrorism Squad by the naval command in Mumbai. The Intelligence Bureau units in the three cities were also alerted. The central intelligence agencies suspected Ali Jihad to be an offshoot of the Indian Mujahideen (IM) or the Lashkar-e-Taiba (LeT). The Mumbai Anti-Terrorism Squad also released photographs of four IM members active in Maharashtra who are sought in connection to the Pune blasts of 2010.
US authorities in India are also reportedly on their toes. Though the threat is believed to be a non-credible one, but yet authorities were not ready to take any chance with the standard security procedures at any of the US facilities or for any of their employees.