This is what happens when we have inexperienced contractors who do not follow safety rules and proper control of the work-place.
malaysiakini's report One dead in Malacca mall blast merely states the obvious reason given by the police as "was likely caused by a gas leak".
If you observe most contract workers in Malaysia, you will notice that many are ignorant or just could not care less about safety rules and procedures.
I would suggest that the following would be the likely cause of this tragedy:
1.The supervisor was too inexperienced to be handling the testing of the system.
2.No-smoking ban was not strictly enforced and ignored in the nearby areas.
3.There was no proper testing of the pipe system for leaks with compressed air or other inert gas before the final commissioning.
4.Shoddy workmanship or inferior quality materials were used in the pipeline.
So the minister who promotes unqualified contractors should take notice of this mishap.