Nad’a, I have a different view of this than Gabriel does. At least in American English, “due to” can follow verbs other than “to be.” Example: He ran slowly due to his injury. He screamed due to the pain. Both of these sentences would sound natural and grammatical to an American ear. Also, “Due to” often comes at the beginning of a sentence: “Due to heavy rains, the low-lying areas flooded.” As to “Because of,” Gabriel may be grammatically correct, but in actual everyday speech Americans will use “because of” after the verb “to be”. Example: His anger is because of the way she treated him. The flooding is because of global warming.

Hello, I hope you are doing well. THE RULE "Due to is a predicate adjective + preposition that means “the result of” or “resulting from.” It is always used after a form of the verb to be. E.g. Her headache was due to the enormous elephant peculiarly perched on her head. Because of is a preposition used to introduce an adverbial phrase and means “as a result of.” It is not used after a form of the verb to be. E.g. She had a headache because of the enormous elephant peculiarly perched on her head. THE TRICK Due to has to follow some form of the verb to be." I hope this helps.

Her headache was because of the enormous elephant peculiarly perched on her head. She had a headache, due to last night's events. She wears a garlic necklace, because of the vampires. The werewolves were howling because of the full moon. Due to the fact that I can't think of any examples of when they're not, I believe they are interchangeable. I agree with John.