TC informed external smoke pre alarm atRear M1 car. Staff(LVR) checked and confirmedno heat no sm oke found. ~~~~~ 1683 TC informed external smoke pre alarm. Staff(LVR) checked and confirmed  no heat no smoke found.  1684 found no FC registered during 3 weekly inspection. Found Car 1683 with FC 721 (Smoke External) happened once. Further checked on both cars External smoke detectors & found no water ingressed. Cleaned smoke detector sensors as a preventive measure. Monitor for 5 hrs & found no fault reoccurance.  Aminur/Azmi 44199