(Since we first posted this news, the deaths of four Americans has been confirmed. Scroll down to see our original post and later updates.)
"The four Americans aboard a yacht hijacked by pirates off the coast of Somalia are dead," CBS News' national security correspondent David Martin reports.
CNN is also saying it has been told by Defense Department officials that the Americans have been killed.
"The yacht Quest was hijacked on Friday off the coast of Oman, but is now in the waters between Yemen and northern Somalia. ...
"The organizers of an international yacht race called the Blue Water Rally said the Quest had been taking part in the race but left it Feb. 15 to chart an independent course from India to Oman.
"The Quest is owned by Scott and Jean Adam, a couple from California. The Blue Water organizers also identified the other two Americans onboard as Phyllis Mackay and Bob Riggle. The NBC TV station in Seattle, Washington spelled the name as Phyllis Macay and said she and Riggle are from Seattle."
CBS News adds that earlier today:
"The Quest was being piloted toward the Somali coast — and was being shadowed by a U.S. Navy warship. CBS News national security correspondent David Martin reports that gunshots aboard the yacht were heard, and the warship took action. All 4 Americans were dead, killed apparently by their captors."
"For nearly a decade, Scott and Jean Adam's home had been the 58-foot custom-made sloop the Quest. Although they docked every so often in Marina del Rey to pick up mail and see friends, the couple spent most of their time sailing to far-flung locales such as the Galapagos Islands, Tahiti and New Zealand.
"Posting photos and information on their website, they raved about their travels aboard the Quest. 'We've decided to ... explore Fiji like petals on a flower,' they wrote about their 2007 trip to the South Pacific.
"Now, 'This is all of our worst nightmares,' said Scott Stolnitz, a friend of the couple."
Update at 10:40 a.m. ET: NPR's Frank Langfitt just noted on Morning Edition that in the past, when negotiations have been underway with Somali pirates "usually those negotiations go on for a very long time." What happened in this case to bring the situation to such an awful end remains to be seen.
Update at 9:25 a.m. ET. United States Central Command has posted an account of what happened, confirming the news. It begins:
"At approximately 1 a.m. EST today, while negotiations were ongoing to secure the release of four American hostages, U.S. forces responded to gunfire aboard the pirated vessel (S/V) Quest. As they responded to the gunfire, reaching and boarding the Quest, the forces discovered all four hostages had been shot by their captors. Despite immediate steps to provide life-saving care, all four hostages ultimately died of their wounds."
It also reports that "two pirates died during the confrontation and 13 were captured."