why to find out reasons for late coming? when you have been conveyed that office timing is 9.00 a.m. to 5.00 p.m., it is your duty/responsibility to be in time in office. Let the reasons be no proper conveyance, bus late, got up late in the morning, to drop children at school by 8.40 a.m., and whole lot of reasons you may have (or you can create your own reasons).
When you were selected for the job, were you not informed about the office timing? You have agreed for that? Then why do you expect employer to find out reasons for your inability to be in time? My point is very simple. If office timing is such and such, then you are bound to be in office in time, nothing more.
Now, taking action against erring employes (late comers), is different issue. (When we say late comers, you must remember, there other employees who also reported in time - how they had come to office in time? ) Give them opportunity (whatever system you may adapt - sending circular, counselling, etc.) to correct themselves. In spite of it if they continue to do, deduct their leave (1/2 day probably), if they still continue to do, then go for disciplinary action.
V. Balaji