The murderous reputation of one of Britain's best-known Roman towns has been raised by the discovery of a child's hastily buried skeleton under a barrack room floor.

Archaeologists at Vindolanda fort near Hadrian's Wall are preparing for a repeat of a celebrated coroner's inquest in the 1930s that concluded two other corpses unearthed near the site were "victims of murder by persons unknown shortly before 367AD".

The latest discovery at the frontier settlement in Northumberland is thought to be the remains of a girl aged between eight and 10 who may have been tied up before she died.

Her burial place is reckoned to be almost certain evidence of a crime, according to specialists at the Vindolanda Trust, which has made thousands of finds at the town and its associated fort since the 1920s.

Human burials were strictly forbidden within built-up areas in Roman times, and Vindolanda followed regulations requiring cemeteries to be laid out on the settlement's outskirts. The bones, initially thought to have been those of a large dog, were in a shallow pit dug in a corner of the garrison's living quarters at the heart of the fort.

Patricia Birley, director of the Vindolanda Trust, said: "This definitely looks like a case of foul play. It has been very sad to find a child in this shallow grave under the barrack floor.

"It would have been very difficult to get a body out of the barracks, through the wider fort and out of the gate, but we may never know if the burial took place with or without the collusion of the men who shared the barracks."

The skeleton was identified by Dr Trudy Buck, a biological anthropologist at Durham university, who will now carry out a full autopsy in the hope of establishing a cause of death. This was relatively easy in the 1930s case, when one of the two skeletons found hidden under the floor of a civilian home in Vindolanda's sister-fort of Housesteads had a knife blade slotted between its ribs.

Punishment for any child murder at Vindolanda is obviously impossible, but the guilty party could conceivably be traced in due course. The trust's excavations have produced the earliest and best-preserved written records from the Roman empire, and the unit stationed in the fort at the suspected time of the death – the mid-third century AD – is known to have been the Fourth Cohort of Gauls.