Divers this week began a search of a shipwreck that is “exactly” the size of the Clotilda, the last American slave ship, according to the archaeologist leading the effort to excavate the vessel.

The ship had been found in April by AL.com reporter Ben Raines with the help of the University of Southern Mississippi.

The excavation began Wednesday near Twelve-Mile Island in the Mobile-Tensaw Delta, with divers surveying the sunken wreck and preparing to dredge mud away from the partially buried hull. They brought up deck planks, beams, metal nails and fasteners and other items for examination.

This is the third trip by the archaeological team to the site.

“Here’s what we know. It is exactly the same size as (the Clotilda) in the Registry. Not only in terms of the length, but how wide it is,” said James Delgado, who is leading the National Geographic-funded exploration of the shipwreck. Delgado was speaking at a public quarterly meeting of the Alabama Historical Commission held at Fort Morgan a week ago. The meeting represented his only public remarks on the ship.

“The possibility, not the probability, but the possibility, is this may be Clotilda.”

The shipwreck is near the bank, with the shallowest portions of the wreck about five feet below the surface.

Delgado provided caution about what might, or might not, remain in the hold of the ship, if it is Clotilda. That’s due partly, he said, to the fact that the Clotilda was not a purpose-built slave ship with built-in manacles, as the American slave trade had been outlawed for fifty years.

Delgado speculated at the time that the ship’s hold might still feature stacks of shelving to accommodate 110 captives in a small space.

During the dig on Thursday, the dive team expressed concern about dredging mud out of the wreck due to the large amount of structure they found in the hull. It is unclear what that structure is, beyond being man-made and built of wood, but the concern was that the mud might be supporting the structure, and if the mud was removed, things might fall on a diver, trapping them in the hold. The exploration was complicated by recent rains, which have left the river so muddy it is impossible to see anything. The divers described conditions as “diving by braille.”

One of the items brought to the surface for examination was a large iron pipe section with hand-carved threads, as on a giant bolt. At the time, Delgado could be overheard discussing with the dive team that the piece looked like something off a barge. But shipwright Winthrop Turner, who examined photos of the piece taken by AL.com, said it looked like just the right size and shape to be a piece of the capstan, a device used to raise the anchor on a schooner such as the Clotilda. In the 1800s, capstans were usually made of iron. The piece found by the divers was recovered about 10 feet back from the bow of the wreck, just about where a capstan would sit on the deck of a ship.

At the dig site, Delgado said he would be unable to answer any questions or comment about the ongoing work due to a non-disclosure agreement both he and officials with the Alabama Historical Commission signed with National Geographic. Officials with the Alabama Historical Commission said the agreement prevents them from sharing information with the public about the find until National Geographic publishes an article about the ship.

This is the second shipwreck discovered by AL.com this year. Archaeologists originally believed the first ship found by the news organization in January might be the Clotilda and launched an investigation involving the Smithsonian Institution, the Slave Wrecks Project, the National Park Service, Diving with a Purpose, the Alabama Historical Commission and Search Inc., a private archaeology company.

After that wreck was shown not to be the Clotilda, AL.com partnered with the University of Southern Mississippi to do a comprehensive, hi-tech survey of the section of the Mobile River where Al.com’s original reporting suggested the wreck might lie. The AL.com and University of Southern Mississippi expedition was apparently the first survey of that section of the river using modern technology, according to Delgado.

That survey, conducted in April, revealed 11 potential candidate wrecks in the two-mile stretch of river where a journal kept by the Clotilda’s captain suggests the ship was burned after illegally smuggling 110 African captives into the country to enslave them in 1858.

Following the survey, AL.com reporter Raines and Monty Graham, head of marine sciences at the University of Southern Mississippi, explored several of the wrecks discovered in the survey. Of those, only one wreck was the right size and made of wood, instead of metal.

After exploring that wreck, AL.com identified it as a ship from the middle 1800s, matching the approximate size, age, and construction techniques of the Clotilda. Next, AL.com informed the Alabama Historical Commission of the find, providing all of the University of Southern Mississippi search data. That data included a full bathymetric survey showing the contours of the river bottom and wrecks. It also included a magnetometer survey, recording metal objects in the river, and a sub-bottom profile survey, which revealed objects lying below the river mud.

The University of Southern Mississippi survey was conducted by the Hydrographic Science program in the School of Ocean Science and Technology. It was led by Max van Norden, Dr. Anad Hiroji, Marvin Story, Kandice Gunning, Ashley Boyce, Jennifer Rhodes and Alex Hersperger.

Two days after receiving the data, a news release from the Alabama Historical Commission announced that Search Inc., would follow on the USM survey. That led to another expedition to the river three months later in July, this time involving the National Geographic Foundation and the organization’s chief archaeologist, Fredrik Hiebert, in addition to the Slave Wrecks Project, Search Inc., and the historical commission. That effort was focused primarily on exploring the wreck found by AL.com and Southern Miss.

During that trip, Delgado visited the site of the wreck for the first time with Raines, who showed him three pieces of the ship in shallow water. Later that day, the archaeologists dove the wreck for the first time and collected samples.

No results were released after the July visit due to the non-disclosure agreements. But in the historic commission meeting Delgado said his team had since made another trip to the site to collect more samples. He said the wreck is made of pine and oak, the same types of native Alabama trees that the Clotilda was made of, according to the ship’s registry license issued when the Clotilda was built.

Delgado’s presentation at the historic commission quarterly meeting provided much new insight into the earlier visits to the ship and the decision to excavate it.

“As we’ve assessed it at this point, this is the most logical target to now look at and now test and see what it is,” Delgado said. “But I still want to come back and caution everybody, particularly with something as powerful as the story of Clotilda. We want to take this slow and carefully, and be the best scientists and CSI people we can be. And in that, we want to find as many points of convergence as we can. Having said that, my job as a scientist is to look at it very carefully and prove it is not Clotilda.”

The story of the Clotilda is an unusual one. Beginning in 1808, only the children of existing slaves already in the United States could be forced into servitude. President Thomas Jefferson signed the law that outlawed the importation of Africans.

The law was a point of contention to many in the South, who feared it would hasten the end of slavery in the country. Timothy Meaher, a Mobile, Ala., steamboat captain and plantation owner made a bet that he could sneak a load of 100 slaves into the country, despite the federal law.

His nefarious mission was successful, but he and the captain of the Clotilda, William Foster, were so scared of being found out by the authorities, that they decided to burn the Clotilda at the end of the voyage to hide the evidence of their crime.

The most compelling part of the story of the Clotilda includes the fate of the captives, who were freed just five years after they were enslaved, thanks to the end of the Civil War. The group, 110 strong, originally asked their captor, Meaher, to pay for passage back to Africa. After he refused, they appealed to the U.S. government, again to no avail. Ironically, they were ineligible for help, federal officials decided, because there was no record of their enslavement, which of course had been kept secret from the government. Ultimately, some members of the group bought a small piece of land north of Mobile from Meaher and created a community called Africatown, where some of the descendants of the original slaves still live. They spoke their native tongue, farmed using traditional African methods, and ran their own school.

Descendants of those brought to this country aboard the Clotilda are believed to be the only group of slave descendants who know precisely where their ancestors came from, when they arrived, and what vessel brought them here.

Historian Sylvianne Diouf traced the evolution of the wicked scheme and the resulting journey in her excellent book, “Dreams of Africa in Alabama,” published in 2007.

AL.com concentrated its search on an area surrounding Twelve-Mile Island in the Mobile River, a few miles north of the port of Mobile after reviewing dozens of primary historical sources. The two most important documents include a 13-page, hand-written description of the entire journey of the Clotilda written by Foster, and a newspaper interview with Meaher, that was written for a New Orleans paper 30 years after the Clotilda arrived. Those sources differ on the critical detail of where the ship was burned, though they agree that it was Foster who did the burning. Both sources put the burning within about a mile of the spot AL.com found both ships discovered this year.

Aside from being the exact size of the Clotilda, another powerful piece of evidence is the location of the wreck. A member of the Meaher family said that his ancestors owned a huge tract of land around Twelve-Mile Island beginning in the 1850s. That’s important because the historical accounts of the Clotilda report that the captives were forced off the ship before it was burned and hidden in the swamp next to Twelve-Mile Island. They were forced to live in the snake and alligator infested swamp for two weeks before being split up and moved to three different plantations.

“What will we find? It’s hard to say. I’ll just cut to the chase. A lot of people think we are going to dig in this and we are going to find shackles. I don’t necessarily think so, even if this is Clotilda,” Delgado said. “I doubt we would see anything of that sort. In terms of other evidence, the shelving built to accommodate people, the casks for food and all the rest, that might be there… It may be that if this is Clotilda, a fair amount got burned. It may be that as it sank we might not see any evidence of the burning because as the river swept through it may have carried a lot of that away. So in short, I want to be right up front. We may never be able to say that this is Clotilda, but at this point, I can’t say that it’s not.”