Ellipsis at the end of a quote [duplicate]

Possible Duplicate:
Punctuation of direct speech, edge cases
Space before three dots?

"I don't think so," she stated.

"I don't think..." her voice trailed off.

Is this second sentence correct from punctuation point of view (ellipsis working along with the same rule as ?,! - replacing the comma), or does it require an extra comma? (or yet something different?)

I'm aware it is normally used instead of a comma or a full stop, with very rare exceptions, but the rules of using punctuation at the end of interrupted quotes still baffle me.

Solution 1:

"I don't think so," she stated.

"I don't think..." her voice trailed off.

You have punctuated correctly. In the first sentence, the comma is essential in that it sets off an attribution--one without which, the end of the quotation, or even its presence, would be unclear (to a listener).

In the latter sentence, clearly, her voice trailed off is not an attribution but, simply, a phrase the modifies the preceding phrase that just happens to be, but need not have been, a direct quotation.

The latter sentence with quotation could have been written: "I don't think...," she said as her voice trailed off. In which case the attribution would not have been implicit.

Yours is an example where speech cannot always follow writing without ambiguity or without clear speech context, such as in story telling.