Sometimes the wire services will keep the same URL but change the text in the story and even the headline as more facts become available.
I had this happen to me a few years ago on a story I submitted about Fedex misplacing some radioactive rods.
By the time the story was posted the rods had been found and the linked story was a non-story with a new headline:
"FedEx Finds Radioactive Shipment That Vanished Between N.D. and Tenn."
Some newspapers like the NY Times will post a correction at the bottom of the story whenever something changes in the story.
"Go to Heaven for the climate, Hell for the company." -- Mark Twain