Thanks Lal. I went through the suttas.
Siebe said; But if one would zoom in and look for a cause for a certain illness or pain or suffering one must be careful to immediately think that must be due to kamma.
In the Pubbakamma Pilotika Therapadana (THA AP392) in the Kuddaka Nikāya, the Buddha specifically mentions the causes for pain and illnesses he suffered after becoming the Buddha.
For example; in a previous birth he had killed his step-brother by throwing him off a rock to get his father’s wealth. Due to this kamma-vipaka his foot was injured when Devadatta threw a rock at him and it hit another rock and a splinter hit him.
From this it is obvious that the root cause is kamma, but other 7 causes may also come together for the vipaka to manifest.
With regard to natural disasters; if people dying by such natural disaster isn’t due to kamma vipaka how else can we explain why only some people are affected and others are not by the same incident? There are people who miraculously survive even when they are in the same place at the same time as others.
Also when a group of people are affected together it is due to all of them being part of a kamma together in a previous time. For example in the Pubbakamma Pilotika Therapadana the Buddha says how he in a previous life insulted a Brahmin and told 500 of his followers the same and all of them went around spreading bad words about the Brahmin. Due to this kamma-vipaka all 500 of his followers in that life, who were ordained and were followers of the Buddha now, were insulted together by Sundarika Pribrajika.