Heavily armed Quick Reaction Teams (QRTs)and dog squads have been deployed at major stations

The city's rail security apparatus has been put on high alert after intelligence agencies warned that terrorists may try to derail trains in parts of the country around Republic Day. Intelligence sources told mid-day that the terrorists — suspected to be radicalised by the Islamic State — may fill expansion joints of the tracks with hard substances like cement or stones at unmanned stretches. Expansion joints have a small gap to allow the tracks to expand during summertime. Inserting a hard substance in these gaps will prevent the tracks from expanding and could result in rail fractures, the sources said.