A colleague and I had a discussion about the use of due to versus because of. We're wondering which one is correct in the example below and why.
This is a complex question—the grammar books we consulted have conflicting views.
In your example, due to/because of is used as a compound preposition introducing an adverbial phrase that modifies the verb kept. While the use of due to as a compound preposition meaning because of is well established, traditionalists have not accepted it as being grammatically correct.
The majority of references we looked at say due to can be used as you suggest in your example, but only in informal writing.
Some say that due to should introduce an adjective phrase (modifying a noun) while others say that due to can be treated as either an adjective or a preposition. The Gage Canadian Dictionary (2003) explains as follows:
The Handbook for Writers, Oxford's Guide to Canadian English Usage, and A Canadian Writer's Reference back the Gage's point of view, explaining that due to normally follows a linking verb ("to be") and functions as an adjective. Because of is used to modify a verb (but not a linking verb).
So to sum up, if your example is in an informal text, you have the choice between because of or due to. For more formal writing, use because of or rephrase the sentence if you want to use due to. Your example would be rewritten something like this: