still remains unknown

[joham]

In my textbook there's a sentence like this:

The cause of the accident still remains unknown to us.

I wouldn't think the word 'still' is necessary here since 'remains' means 'is still'. Am I right? Thank you.

[Anglika]

Not quite.

remain = to stay in the same place or in the same condition.

You can still remain at the end of the term >> You can still stay in the same place at the end of the term >> you can continue to stay in the same place...

The evidence still remains unclear >> The evidence is still in the same condition of not being clear.