The correct answer is - lead.
Southeast Asia is a region that is abundant in natural resources. One of those resources is the lead. The lead has initially been heavily used in making pencils, though over time it has been replaced by the graphite which is more practical and not very dangerous for the health.
Even though some companies still use lead for the pencils in the present, that is very rare, and the reason for that is that the lead is extremely toxic, so the graphite took its place.