Where there is smoke there is fire, but not always. On Wednesday evening, smoke outside Home Minister Rajnath Singh’s room in North Block triggered the fire safety alarm. Singh was in his office then. Security personnel responded quickly. Fire extinguishers were pressed into service. But the security personnel found no trace of fire. The mystery of the source of the smoke remained unresolved. Officials speculated that the smoke could have emanated from one of the staff having lit a cigarette, or a possible spark in the power connections.