Archaeologists have lifted the 700-kilogram lid of a 1,000-year-old sarcophagus hidden under the floor of a cathedral in Mainz, Germany.

Key points: The tomb was found while restoration work was being carried out on the cathedral

The tomb was found while restoration work was being carried out on the cathedral Bones inside the coffin were significantly decayed, but there was enough material for scientists to process

Bones inside the coffin were significantly decayed, but there was enough material for scientists to process It's believed the remains could be those of an archbishop, with gold fragments in the sarcophagus strengthening that theory

A small corner of stone coffin was discovered during restorations on the St Johannis Church in 2017, with specialists working to reveal the entire tomb layer-by-layer.

This week, a team of 14 archaeologists, anthropologists and textile scientists were finally able to lift the heavy lid, in a highly-coordinated effort that required an industrial pulley system.

Research director Guido Faccani said inside were just some scraps of fabric and severely decomposed bone fragments.

"Not even teeth [were] found," he said in a statement from the church.

Mr Faccani said the corpse had probably been doused with quicklime when buried, a process that at the time was thought to speed up the decay process.

A team of 14 experts were on the site as the lid was lifted. ( EKHN )

However, there may be enough material inside the coffin to give researchers enough to clues to make an educated guess at whose remains were laid to rest there.

Researchers will examine the pattern of the cloth to help narrow down the historical era, while scientists will be able to process what remains of the deceased's bones.

An examination with a metal detector picked up gold fragments, believed to be an ornamental embellishment on a liturgical robe.

Gold was also discovered around the head area, suggesting the metal could have been used as part of a ceremonial headdress, possibly being a bishop mitre.

The 700-kilogram lid was lifted using a heavy-duty pulley system. ( EKHN )

The find has strengthened theories the grave belonged to an archbishop known as Erkanbald, who died in 1021.

But researchers said it would take some time to determine just whose decomposed bones lay in the sarcophagus.

"Science lasts as long as it lasts," Dr Faccani said.

However, the grave will not be open for long.

Researchers were aiming to process the site as quickly as possible to reduce the impact of fresh air on the bones.

Once the researchers have completed their examination of the grave, it is likely the remains will be sealed by the stone lid and will continue to rest in the cathedral.