Marine archaeologists have recovered a bronze arm from an ancient shipwreck off the Greek island of Antikythera, where the remains of at least seven more priceless statues from the classical world are believed to lie buried.

Divers found the right arm, encrusted and stained green, under half a metre of sediment on the boulder-strewn slope where the ship and its cargo now rest. The huge vessel, perhaps 50m from bow to stern, was sailing from Asia Minor to Rome in 1BC when it foundered near the tiny island between Crete and the Peloponnese.

The project team, from the Greek Ephorate of Underwater Antiquities and Lund University in Sweden, discovered the buried arm with a bespoke underwater metal detector which has revealed the presence of other large metal objects nearby under the seabed. “There should be at least seven statues,” Alexandros Sotiriou, a Greek technical diver on the team told the Guardian. The operation is overseen by Ageliki Simosi, director of the Greek Ephorate of Underwater Antiquities, which is responsible for all underwater archaeology in Greece.

Facebook Twitter Pinterest Detail of the arm discovered under half a metre of sediment by the ancient shipwreck. Photograph: Brett Seymour/EUA/ARGO 2017

“What we’re finding is these sculptures are in among and under the boulders,” said Brendan Foley, co-director of the excavations team at Lund University. “We think it means a minimum of seven, and potentially nine, bronze sculptures still waiting for us down there.” The boulders that overlie the metal objects weigh several tonnes and may have tumbled onto the wreck during a massive earthquake that shook Antikythera and surrounding islands in the 4th century AD.

The bronze arm, probably from a statue of a male, is the highlight of the team’s 2017 excavation season. Among other objects the divers recovered are a patterned slab of red marble the size of a tea tray, a silver tankard, sections of joined wood from the ship’s frame, and a human bone. Last year, the team found the skull, teeth, ribs and other bones of an individual who perished on the wreck. They have since extracted DNA from the skull and from it learned the individual’s sex and where they came from. Until those results are published, the person is known as Pamphilos after divers found the name, meaning “friend of all”, carved on a buried cup that had been decorated with an erotic scene.

The Antikythera wreck first came to light in 1900 when Greek sponge divers happened on the scene in 50 metres of water. Archaeologists have since pulled up spectacular bronze and marble statues, ornate glass and pottery, stunning pieces of jewellery, and a remarkable geared device – the Antikythera mechanism – which modelled the motion of the heavens. During the 2017 excavations, divers recovered a bronze disc that may be a missing part of the ancient device.

But it is the statues that made the wreck famous. In the 1900s, archaeologists working at the site surfaced pieces of a beautiful Hellenistic bronze, named the Antikythera Youth. The statue now stands in the National Archaeological Museum in Athens alongside an impressive bronze head named the Antikythera philosopher, also hauled from the wreck. Both date to the 4th century BC, raising the question of how they came to be aboard the ill-fated ship 300 years later.

Jens Daehner, associate curator of antiquities at the J Paul Getty Museum in Los Angeles, said the Antikythera wreck had already yielded significant bronze statues. “The chance to recover another group of lifesize statues associated with the wreck is extraordinary, because bronzes are usually encountered randomly under the sea, picked up by fishing nets or chanced upon by divers,” he said. “Those finds are not excavated like at Antikythera, where archaeologists can and do document the entire context, which provides all the sorts of very valuable data as to when the sculptures were transported and why they were on the ship: for trade, as booty, or as scrap metal to be recycled.”

Facebook Twitter Pinterest As well as the arm, divers have recovered a patterned slab of red marble the size of a tea tray, a silver tankard, sections of joined wood from the ship’s frame and a human bone. Photograph: Brett Seymour/EUA/ARGO 2017

The bronze recycling industry was huge in classical times and later in the medieval period, leading to the destruction of countless statues and other artefacts that would be priceless today. For this reason, many of the finest specimens of bronze statues that survive were once lost at sea. “Ancient bronze sculpture in general is rare due to the metal having been recycled in antiquity and later. We think of the ones from the sea as those that got away,” said Daehner. “Any chance to recover more Greek sculptures in any medium, but particularly in bronze, should not be missed.”

To recover the statues will take a massive effort. The divers must first remove boulders that are in their way, either by hauling them up, or by drilling holes in the rocks and filling them with grout that expands to fracture the stone. Another option is to crack the boulders open with small shaped charges that technical divers use to rescue people trapped when undersea caves collapse. But even if the statues can be lifted from the sea, they will be broken and need costly and time-consuming conservation and reconstruction.

Statues are not the only objects the excavators hope to find. The latest excavations uncovered a lump of material bearing a bronze disc that matches the size of geared wheels found in the Antikythera mechanism. Wound by a handle, the device showed the movement of the sun, moon and planets in the sky, but not all of the machine was recovered. “The disc looks very exciting indeed,” said Andrew Ramsey, a CT specialist at Nikon Metrology in Tring, who used CT scans to read inscriptions on the original pieces of the mechanism. But the disc may be something entirely different. Preliminary x-ray images reveal no teeth, but an image of a bull, suggesting the disc is not a cog but a decorative item.

Facebook Twitter Pinterest Divers also discovered this piece of material bearing a bronze disc that matches the size of geared wheels found in the Antikythera mechanism. Photograph: Brett Seymour/EUA/ARGO 2017

Mike Edmunds, emeritus professor of astrophysics at Cardiff University and a member of the Antikythera Mechanism Research Project, said the findings are impressive. “They are getting very good at detecting bronze items which raises the possibility that they may be able to find either the missing planetary gearing from the Antikythera mechanism, which we know is there from the analysis of the inscriptions on the mechanism, or a new piece of mechanism, or another mechanism that was being transported, and that would be very exciting.”

The team will return to the wreck in the spring, optimistic that they may pull up fresh treasures from the wreck. “It’s not going to be just the bronze sculptures,” said Foley. “We’re down in the hold of the ship now, so all the other things that would have been carried should be down there as well. Every day is going to be like opening Tut’s tomb.”