1. because of 用于表示引起事件发生的直接原因：

Because of their high vitamin and low calorie content, mushrooms are included in certain diets (TOEFL).由于蘑菇含有极高的维生素和极低的热量，所以有一些保健食品放入了蘑菇。（摘自《英语常见问题解答大词典》）

2. 2008年7月第1版《外研社英汉多功能词典》指出：表示“由于；因为”的意思时，因常有误用的情况，现在 due to 与 because of 、owing to 用法相同。（p.638）

3. 传统语法认为：due to引导的短语只能作表语或者后置定语，不能作状语；because of 引导的短语只能作状语，不能作表语。

但是，在当代英语中，上述限制已经被打破了。

(1) 以考核学生标准书面英语能力的TOEFL也常常使用 due to 引导的短语作状语，即用 due to 来代替 because of 或 owing to：

Only three new sites were built in this city due to a decrease in business activity and prices rising. (TOEFL) 这道题的答案是把 prices rising 改为 an increase in prices, 而 due to 没有错误。（转引自赵振才：《英语常见问题解答大词典》增订版第四版）

(2) 以下是摘自英美等国权威的英语词典和语法著作的例句：

Joe's applicationto the university was not accepted due to his failing English. (A Dictionary of American Idioms by M. T. Boatner, J. E. Gates, et al, 1975)

He was late due to an accident. ( The Concise Oxford Dictionary of Current English by H. W. Fowler and F. G. Fowler , 1976 p.320)