Direct Material Cost doubt

In the Cost Accounting module for IPCC(Material Capter), they have explained resons as to how Direct Material Costs can increase. I have a doubt in 2 of them:

*Interruption in the flow of materials and hence resuting in stoppage of machines.

*Over stocking of materials.

I understand how they both direcly affect the Total Cost of the firm. But i'm not understanding how they both increase the Direct Materials Cost. Please clarify :)