Nuclear installations across the country have been put on high alert as it has been found that David Headley, a US citizen arrested by FBI on terror charges, had visited these places. Sources in the Home Ministry said on Monday that all the states having nuclear plants have been asked to step up patrolling and vigil around the facilities as a precautionary measure.<br/>Headley, accused of plotting terror attacks in India on behalf of Pakistan-based LeT, had visited Gujarat, Maharashtra and Uttar Pradesh all having crucial nuclear installations , raising suspicion that nuclear facilities could be on the radar of the terrorists.<br/>AIR correspondent reports,there are six major nuclear energy plants operational in the country, Narora in Uttar Pardesh, Kaiga in Karnataka, Tarapur in Maharashtra, Kalpakkam in Tamil Nadu, Kakrapar in Gujarat and Kota in Rajasthan, besides several other Research and Development centres like Bhabha Atomic Research Centre in Trombay.<br/>AIR correspondent Manikant Thakur reports that with fresh revelations and several evidences on hand , the Home Ministry has directed the state governments, particularly Maharashtra, to beef up security around the atomic facilities as the terrorists may target them. The arrested Pakistan-born US Terror mastermind David Headley and LeT OPERATIVE Tahawur Rana had made a requee of these areas. The Bhabha Atomic Research Centre (BARC), located in Mumbai has been put on the highest alert. The Indian Navy, Coast Guard and all other security agencies have been directed to take precautionary measures to protect such installations as majority of them located on the sea coast. <br/>The government today said all nuclear installations are absolutely secure. The Minister of State in the Prime Minister's office Mr. Prithviraj Chavan said that there are multiple levels of security. His remarks came in the wake of reports that Centre has asked the state governments having nuclear installations to tighten security around such facilities to foil any possible terror attack.