A search is on to trace the four men, police said.According to Indian Navy Chief PRO Capt D K Sharma, the search operation is going on along with Maharashtra police after the matter came to light.The Western Naval Command (WNC) issued "the highest state of alert" along the Mumbai, Navi Mumbai, Thane and Raigad coasts after suspicious movement of a group was reported in Uran.The WNC has roped-in the police and Coast Guard also for the task.According to initial information received by the authorities, four school students in the morning spotted a group of people dressed in uniform similar to that of Indian Army near Uran and Karanja area. The teenagers immediately informed the school authorities following which the local police were tipped."ONGC" and "school" were two words that the students overheard the men wearing black masks as saying.The DGP office immediately issued alerts to all police stations along the coast.Security has been beefed up at sensitive locations along the coast, including the Gateway of India, Raj Bhawan, Bombay High (rig), Bhabha Atomic Research Centre and other major establishments near the sea.