Prime Minister Stephen Harper says one of Canada's greatest mysteries now has been solved, with the discovery of one of the lost ships from Sir John Franklin's doomed Arctic expedition.

"This is a great historic event," Harper said.

"For more than a century this has been a great Canadian story.… It's been the subject of scientists and historians and writers and singers. And so I think we have a really important day in mapping together the history of our country," the prime minister said.

At this point, the searchers aren't sure if they've found HMS Erebus or HMS Terror. But sonar images from the waters of Victoria Strait, just off King William Island, clearly show wreckage of a ship on the ocean floor.

Franklin Ship found

A sea floor scan reveals one of the missing ships from the Franklin Expedition in an image released in Ottawa on Tuesday. (Parks Canada/Canadian Press)

The wreckage was found on Sept. 7 using a remotely operated underwater vehicle recently acquired by Parks Canada. When Harper revealed the team's success at Parks Canada's laboratories in Ottawa Tuesday, the room burst into applause and hollering. 

"This is a day of some very good news," Harper told the assembled group of researchers, some of whom had flown all night to be in Ottawa for the announcement. 

"It appears to be perfectly preserved," Harper said of the ship, adding that it has "a little bit of damage."

Deck appears intact

Harper said the "latest, cutting-edge technology" Parks Canada used was integral to finding the ship under layers of growth on the ocean floor. "With older technology, you could have come very close to this and not seen it at all."

Ryan Harris, an underwater archeologist who was Parks Canada's project lead for this year's search, said the wreck was "indisputably" one of Franklin's two ships.

"It's a very substantial wreck," Harris said, putting to rest earlier fears that Franklin's ships may not be found intact after so many years.

The sonar image shows some of the deck structures survived, Harris explained, pointing out the stubs of the masts which were apparently sheared away by the ice when it sank.  Because the deck is relatively intact, the contents of the ship "should be very, very well-preserved."

The next step for the search team will be to take a look at what's inside.

Discovery 6 years in making

In a statement, the prime minister said Franklin's expedition laid the foundations of Canada’s Arctic sovereignty.  He called the lost ships Canada's "only undiscovered national historical site."

The prime minister paid tribute to the search teams — a partnership between Parks Canada, the Royal Canadian Geographical Society, the Arctic Research Foundation, the Canadian Coast Guard, the Royal Canadian Navy and the government of Nunavut — whose work since 2008 has paid off.

Franklin discovery locator map

“This discovery would not have been possible without their tireless efforts over the years, as well as their commitment, dedication and the perseverance of the many partners and explorers involved," Harper said.

Queen Elizabeth sent a message for Canadians to the Governor General on Tuesday following the discovery.

"I was greatly interested to learn of the discovery of one of the long-lost ships of Captain Sir John Franklin. Prince Philip joins me in sending congratulations and good wishes to all those who played a part in this historic achievement," she said in a statement.

Franklin's crew became locked in the ice during a doomed search for the Northwest Passage to the Pacific Ocean in 1845. All 128 crew members eventually died, though there's evidence to suggest some may have survived for several years.

Many searches throughout the 19th century attempted to find the lost ships, but the mystery of what happened to John Franklin and his men has never been solved.

Search parties later recorded Inuit testimony in the late 1840s that claimed one ship sank in deep water west of King William Island, and one ship went perhaps as far south as Queen Maud Gulf or into Wilmot and Crampton Bay. The location of this wreck backs up that testimony. 

Artifacts found first

On Monday, the government of Nunavut announced that two artifacts from the Franklin expedition were found on an island in Nunavut.  

A team of archeologists had found an iron fitting from a Royal Navy ship, "identified as part of a boat-launching davit, and bearing two broad arrows," on an island in the southern search area, the territory's government said.

Franklin expedition ship

An iron fitting from a Royal Navy ship, identified as part of a boat-launching davit and bearing two broad arrows, was found on an island in the southern search area. (Douglas Stenton, Government of Nunavut)

A wooden object, "possibly a plug for a deck hawse, the iron pipe through which the ship’s chain cable would descend into the chain locker below," was also found.

"The iron fitting was lying on the shore, adjacent to a rock, a large rock, and the wooden artifact was a bit farther away, a bit farther from the shoreline," archeologist Doug Stenton told CBC News.

Stenton headed a three-member Nunavut team that found the objects on an island in the Queen Maud Gulf near Nunavut's King William Island on Sept. 1.

The searchers said these were the first artifacts found in modern times. Now they've pointed the way to the bigger find.

Inuit history accurate

"The beauty of where they found it is it's proof positive of Inuit oral history," CBC chief correspondent Peter Mansbridge, who has covered the Franklin search for many years, said Tuesday.

"The Inuit have said for generations that one of their hunters saw a ship in that part of the passage, abandoned and ended up wrecking…. It's exactly where this guy said it was."

The question now is whether these discoveries bring the project closer to finding more evidence of what happened to the Franklin expedition.

“Finding the first vessel will no doubt provide the momentum — or wind in our sails — necessary to locate its sister ship and find out even more about what happened to the Franklin expedition’s crew,” Harper said in his statement.

With files from The Canadian Press