Workers excavating at the World Trade Center site have unearthed the 32—foot (9.75—meter)—long hull of a ship likely buried in the 18th century.

The vessel probably was used along with other debris to fill in land to extend lower Manhattan into the Hudson River, archaeologists said.

Archaeologists Molly McDonald and A. Michael Pappalardo were at the site of the September 11, 2001, terror attacks on Tuesday morning when workers uncovered the artefacts.

“We noticed curved timbers that a backhoe brought up,” Ms. McDonald said on Wednesday. “We quickly found the rib of a vessel and continued to clear it away and expose the hull over the last two days.”

The two archaeologists work for AKRF, a firm hired to document artefacts discovered at the site. They called Tuesday’s find significant but said more study was needed to determine the age of the ship.

“We’re going to send timber samples to a laboratory to do dendrochronology that will help us to get a sense of when the boat was constructed,” said Ms. McDonald, who added that a boat specialist was going to the site on Thursday to take a look at the ship. Dendrochronology is the science that uses tree rings to determine dates and chronological order.

The workers and archaeologists also found a 100—pound (45—kilogram) anchor in the same area on Wednesday, but they’re not sure if it belongs to the ship.

The archaeologists are racing to record and analyze the vessel before the delicate wood, now exposed to air, begins to deteriorate.

“I kept thinking of how closely it came to being destroyed,” Mr. Pappalardo said.

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