Image caption Who the victims are or which side killed them remains unknown

Sri Lankan experts say a mass grave found earlier this year in the north-western town of Mannar has turned out to be the country's biggest such site.

More than 230 skeletons have now been found at the grave in the former war zone, up from about 90 in August.

Human rights groups say at least 20,000 people disappeared during Sri Lanka's long civil war which ended in 2009.

The 26-year war between troops and separatist Tamil rebels left at least 100,000 people dead.

A court ordered detailed excavations at the site - a former co-operative depot near the main bus terminus - after human remains were found by workers digging foundations for a new building earlier this year.

It is still not clear who the victims were or how they died.

"We have excavated more than 230 skeletons so far," said Professor Raj Somadeva, a forensic archaeologist from the University of Kelaniya near Colombo who leads the team at the site. "According to my experience this is the largest mass grave ever excavated."

He said that apart from the human remains, the archaeologists had also found porcelain, ceramic and metal objects, in addition to some jewellery worn by the victims.

"The bones are scattered and [it's] very difficult to trace the stature of the bodies," Prof Somadeva told the BBC. "And some bones were missing…it's chaotic."

The town of Mannar is dominated by ethnic minority Tamils and community leaders says hundreds of people from the region went missing during the decades-long conflict between Sri Lankan security forces and Tamil Tiger rebels.

While Mannar town remained mostly under army control during the civil war, Tamil Tiger rebels dominated its surrounding areas and many other parts of the district. The military captured the entire district after ferocious battles which ended almost 10 years ago.

Image copyright AFP Image caption Many people were taken into custody during the conflict and thousands disappeared

After the remains are uncovered, they are transferred to the custody of the court in Mannar, which will decide what should happen next once the excavation is complete.

A number of mass graves have been unearthed in Sri Lanka's former war zone since the conflict ended.

The remains of 96 people were discovered in 2014 at a site in another part of Mannar - adjacent to Thiruketheeswaram, a prominent Hindu temple.

But four years on there's still no clarity in that case either, about who was killed and by whom.

Rights groups allege that both the military and the defeated Tamil Tigers inflicted widespread civilian casualties.

But the government has always denied its forces had anything to do with civilian deaths or disappearances, and the army dismisses any suggestion that soldiers are connected with the bodies found in the mass graves in Mannar.

After years of international pressure, the government earlier this year set up an independent body, the Office of the Missing Persons (OMP), to investigate the disappearances. The OMP has provided partial funding for the excavation in Mannar.