《朗文》名词help用法：

help2 ●●● S1 W1 noun    

1 [uncountable] things you do to make it easier or possible for someone to do something 

Thank you for all your help.

help with something/with doing something 

Do you want any help with the washing up?

help to do something 

I could do with some help to bring the bags in from the car.

help (in) doing something 

He asked for my help in getting an interview with her.

以上名词help用法表明，help既可以后接to do不定式，也可以后接in doing, 而且介词in是可以省略不用的。所以，美国之音文章并没有错。这里用 to investiggate 和 （in）investiating意义相同。