Use of の with かもしれない


> 北海道の海岸に向かう途中で、川に入ってしまった **の** かもしれません。  
>  They might have ended up entering the river en route to the Hokkaido coast.

What is の (in bold) doing in this sentence? It was my understanding that
かもしれない came straight after the predicate.

My guess is that this is the so-called 'explanatory の' rather than a
nominaliser. Please can you confirm or correct my thoughts?




Yes, this is a typical example of
[explanatory-の](https://japanese.stackexchange.com/q/5398/5010). Looking at
the
[source](http://www3.nhk.or.jp/news/easy/k10011292341000/k10011292341000.html),
we can see this sentence is trying to explain _why_ the アザラシ was found in the
mountain.

>   * 川に入ってしまいました。  
>  The animal ended up entering the river.
>   * 川に入ってしまったのです。  
>  It is that the animal ended up entering the river.
>   * 川に入ってしまったかもしれません。  
>  The animal may have ended up entering the river.
>   * 川に入ってしまったのかもしれません。  
>  It may be that the animal ended up entering the river.
>




Yes, this is a typical example of
[explanatory-の](https://japanese.stackexchange.com/q/5398/5010). Looking at
the
[source](http://www3.nhk.or.jp/news/easy/k10011292341000/k10011292341000.html),
we can see this sentence is trying to explain _why_ the アザラシ was found in the
mountain.

>   * 川に入ってしまいました。  
>  The animal ended up entering the river.
>   * 川に入ってしまったのです。  
>  It is that the animal ended up entering the river.
>   * 川に入ってしまったかもしれません。  
>  The animal may have ended up entering the river.
>   * 川に入ってしまったのかもしれません。  
>  It may be that the animal ended up entering the river.
>

