(CNN) -- An underwater explorer who says he's confident he's discovered the Santa Maria, Christopher Columbus' flagship, said Wednesday that there's evidence that the ship has been looted.
During a news conference, 68-year-old Barry Clifford said that the remains of the possible ship off the coast of Haiti probably hold "a great deal of cultural material" but that he and his team of divers can tell that thieves have disrupted the wreck and taken things.
When asked when the ship might have been looted, Clifford said he didn't know. "Something might have been done several months ago, maybe a couple years ago, I'm not sure," he said.
Clifford says he wants the Haitian government to act as soon as possible to help preserve the what he says is the ship's remains.
He also wants the Haitian government to give him permission to continue to study the wreckage. "I'm not looking for money," Clifford said. "I'm looking for the government (of Haiti) to protect this."
He said that whatever his team does next must be coordinated through the Haitian government.
A CNN team was in Haiti on Wednesday and asked the senior adviser to the country's prime minister about Clifford's claims.
Adviser Damian Merlo said in an e-mail that officials did not know whether the wreck was indeed the Santa Maria.
Merlo said Prime Minister Laurent Lamothe said that if Clifford's claims are correct, "it would be of great importance, not only for Haiti, but for world history."
"We need to ensure the site is handled properly to protect any archeological findings," Lamothe said, according to Merlo.
Clue from another wreck
Clifford is an experienced explorer, according to the History Channel website, which described him as "one of the world's premiere underwater archaeologists."
His assertion that he's probably found the Santa Maria is tied to a shipwreck he and his team investigated in 2003. A cannon was found as part of the first wreck. But, Clifford told CNN, archaeologists at the time "misdiagnosed" the cannon.
Two years ago, after having researched the type of cannon used in Columbus' time, "I woke up in the middle of the night and said, 'Oh, my God,' " Clifford said. He realized the 2003 find might have been the one.
A couple of weeks ago, he returned to the wreck with a group of experts. The team measured and photographed the ship. But some items, including the cannon, had been looted from the ship in the intervening years, Clifford said.
The ship "still has attributes that warrant an excavation to determine the site's identity," archaeologist Charles Beeker of Indiana University said Tuesday. "Barry may have finally discovered the 1492 Santa Maria."
The evidence, Beeker said, is "very compelling."
The ship was found in the exact area where Columbus said the Santa Maria ran aground more than 500 years ago, Clifford said. The wreck is stuck on a reef off Haiti's northern coast, 10 to 15 feet beneath the water's surface.
Wrecked in 1492
The Santa Maria was the flagship of Columbus' small fleet that set sail from Spain in August 1492 under the sponsorship of King Ferdinand II and Queen Isabella I.
The voyage aimed to find a westward route to China, India and the gold and spice islands of the East. But the land the sailors set eyes on in October 1492 was an island in the Caribbean.
Among the islands on which Columbus set foot was Hispaniola, which is divided between Haiti and the Dominican Republic. Columbus established a fort in Haiti.
That December, the Santa Maria accidentally ran aground off the island's coast. Some planks and provisions from the wrecked ship, which was about 117 feet (36 meters) long, were used by the garrison at the fort, according to Encyclopaedia Britannica.
Columbus set off back to Spain with the two remaining ships, the Nina and the Pinta, in January 1493.
There have been reproductions of those ships, but they are based on vague assumptions. "We don't have very accurate records of what they looked like," he said.
CNN's Danielle Dellorto, Ronni Berke and Miguel Marquez contributed to this report.