'warn of'/ 'warn about'

[GeneD]

I'm trying to tell the difference between 'warn of' and 'warn about', but I'm not sure I understand it correctly.

1) I warned the kids about riding their bikes in the street. (https://idioms.thefreedictionary.com/warn+about)but
2) The kids were warned of/about the dangers of the street.

1) The employees were warned of/about the company's impending bankruptcy. (https://idioms.thefreedictionary.com/warn+of)
but
2) The employees were warned about this company.

The examples in bold were taken from the dictionary I gave the links to. The other I made up myself in order to check my understanding. In the second pair I added 'of' (underlined) because in the grammar book I'm using (by Raymond Murphy) it was said that 'warn of' and 'warn about' can be used interchangeably sometimes, and I'm trying to check if I understand correctly when exactly.

Could you check the examples?

 

[Charlie Bernstein]

They mean the same thing to me. What difference do you see?

 

[GeneD]

Well, I've been struggling to see this difference so hard that I'm not sure it's not a mirage I see.

I'll quote from the grammar book I mentioned:
"1) warn somebody about a person or thing which is bad, dangerous, unusual, etc.
I knew he was a strange person. I had been warned about him. (not warned of him)
Vicky warned me about the trafic. She sat it would be bad.

2) warn somebody about/of a danger, something bad which might happen later
Scientists have warned us about/of the effects of global warming."

Maybe the author means some abstract ideas (circumstances, consequences or something like that) in the second case?

 

[GeneD]

But he's British. (http://www.cambridge.org/ru/cambridgeenglish/authors/raymond-murphy) Maybe in AmE, there's no difference between the two expressions?

 

[Charlie Bernstein]

Hm. Could be. Let's see if any of our other UsingEnglish brothers and sisters have anything to say.

It's true that I'd warn someone about someone else, but I'd also warn someone about global warming. So that's no help.