An archaeological dig under Notre Dame Cathedral has uncovered a treasure of statues, sculptures, tombs and pieces of an original rood screen dating back to the 13th century.

Several ancient tombs from the middle ages and a body-shaped lead sarcophagus were found under the transept crossing monument.

The discovery was described by French experts as extraordinary and emotional.

Under the floor slabs, we found all these riches. It was completely unforeseen. The scientific team for the dig was led by Christophe Besnier, who said that there were exceptional pieces documenting the history of the monument.

It was an emotional moment. We had several hundred pieces from small fragments to large blocks, including sculpted hands, feet, faces, architectural decorations and plants. Some of the pieces were not white.

Part of the archaeological dig at Notre Dame Cathedral

Photograph: Denis Gliksman/Inrap

France's national archaeological institute, Inrap, revealed the discovery on Thursday. A team from the institute was called in to carry out a preventative dig under a section of the cathedral floor between February and April before a 100ft-high 600-tonne scaffold was built to reconstruct the monument.

The original Notre Dame rood screen, an ornate partition between the chancel and nave that separated the clergy and choir from the congregation, has only been Remnants. Some are in the store rooms of the cathedral, while others are in the Louvre. The Counter-Reformation took place in the 16th and 17th centuries. The rest of the Notre Dame rood appears to have been placed under the cathedral floor during the restoration.

An intact sculpture of the head of a man, believed to be a representation of Jesus, is one of the most extraordinary pieces. A block from the rood screen is believed to be from the 13th century.

Head of statue

The head of a statue that experts believe may be Jesus. Photograph: Denis Gliksman/Inrap

The Inrap team was given a specific time frame to carry out the excavation. The 850-year-old cathedral of Paris was almost destroyed in a fire in April, but the president promised to have it rebuilt and open for mass in five years.

Gen Jean-Louis Georgelin, appointed to oversee the restoration, said in September that the safety of the cathedral structure had been established, meaning the restoration and reconstruction of the sections destroyed by fire could begin. He said the cathedral would be open for services and public visits.

Besnier said they had identified several other slabs of the rood screen under the floor, but they were outside the specified limit. He said that they hope to uncover them at a later date.

A network of masonry heating pipes were installed under the floor in the 19th century.

The lead sarcophagus may hold the body of a high church official from the 14th century. There was a camera in the coffin that showed plant remains under the deceased's head, but there was no plate to identify the person.

A sarcophagus containing a human body is not an archaeological object according to the president of Inrap. We must respect the human remains and the sarcophagus while we analyse them.

He said there was no decision on where the body would be reburied. It is possible that it will be reburied in the cathedral.