|• due to|
In careful writing, "due to" is considered to be an adjective, and therefore must modify a noun, not a verb:
"The decline in net profit was due to the higher cost of raw material."In this sentence, "due to" is used correctly, modifying the noun "decline."
Here is a sentence in which due to refers to a verb:
The company's net profit increased due to cost-cutting measures and a decrease in raw materials.