The distinctive blue-coloured glass bottle marked “Hull Infirmary” appears to have been deliberately placed within a grave in Hull. The fully intact sealed bottle also contained a brown liquid which hasn’t yet been definitively identified.

Hull Live reports the bottle was discovered earlier this year as part of the major excavation at the site where burials took place between 1783 and 1861.

A 70-strong team of specialist archaeologists have been working there since last year and are examining around 1,500 exhumed skeletons.

The site is one of the largest post-medieval cemeteries to have ever been excavated in the north of England.

Katie Dalmon, osteology supervisor, said: “It’s quite normal to find artefacts such as rings, coins, items of clothing and even tableware such as plates in a burial plot but this bottle was quite unusual.

“Not only was it apparently specifically placed between the person’s legs but it was also sealed and was nearly full of liquid.”

The inscription on the side of the bottle is a clue that has been used to uncover at least some of the grave’s secrets.

Hull Infirmary was first established in temporary premises in 1782 – a year before the burial ground opened – and then moved to a purpose-built home nearby in 1784.

Katie added: “We now know a little bit more about the identity of the body – it’s a woman who was in her 60s at the time of death. We also know she was suffering from residual ricketts and osteoporosis.

“She was also buried in the middle of a burial stack with the bottle. It was deliberately placed with the individual and was not part of any backfill.”

Tests have also been carried on the mysterious liquid in an effort to establish what it actually is with samples being sent to experts from Nottingham Trent University.

“The tests have confirmed the presence of sodium, potassium and phosphorus and have also discounted any pharmaceutical materials being present,” Katie added.

“The results leave us with the likelihood that the liquid is probably urine but they also raise a whole series of other questions.

“What could this mean? Why was it placed there and, if it’s not urine, what could it be?”

The expert said another theory being examined was that the liquid might have been a type of phosphate-based tonic drink.

She said: “These were popular in the 19th century when they were advertised as a cure for various medical ailments, including tuberculosis.

“We can’t be exactly sure at the moment so we are carrying out more tests to try to get an definitive answer.”

The team from Oxford Archaeology working at the burial ground is expected to spend several years studying all the findings from the site.

Work on the actual site is due to end next month when the remaining giant tents coverng the excavation area will be removed.