Madurai: Critically sensitive are 14 polling stations at five locations. Unlike other districts, Kanniyakumari as a Lok Sabha constituency also goes for by-poll simultaneously along with state polls. There will be heightened security in the vicinity of sensitive and critically sensitive polling stations, SP V Badri Narayanan said. Nine cases have been booked regarding election violations since February 27. The district police have also filed cases against a total of 1,147 persons and among them, 1,076 had signed bonds for maintaining peace.