Security agencies are keeping a close watch on a youth, who was injured in the bomb blast in South Delhi, suspecting that he could be one of the two persons who planted the explosive.Police claimed to have recovered three passports, SIM cards and bag stashed with Rs 500 currency notes from him.The injured, whose identity was not disclosed, was undergoing treatment in the AIIMS trauma centre and would be made available to security agencies for questioning once he had reovered completely, sources said.The injured person was brought from Mehrauli blast site yesterday and he had received injuries in his back.Till yesterday, some people claiming to be the youth's relatives were hovering around the hospital premises but today they seemed to have vanished after security agencies and police started enquiring about the patient.The bomb was placed at Mehrauli suspectedly by two men in their mid-twenties.