Over 80 human bones, including skeletal remains, have been found so far from a mass grave in northern Sri Lanka, the police said on Tuesday. Excavation work was carried out on the grave site in the northern Mannar town after it was first discovered in December last year. The police said that 11 human remains had been found on Monday when excavation work was carried out at the location which was once under rebel control. The police said that the remains have yet to be identified and they have been sent for further investigations. The criminal investigations department is investigating the discovery and there is a suspicion the remains maybe of people killed by the Tamil Tigers during the war. Most parts of Sri Lanka's Tamil-dominated north were under rebel control for the most part of 30 years before the rebels were defeated in May 2009. A UN panel and human rights groups had accused the Sri Lankan military and Tamil Tigers of committing war crimes during the final stages of the war. The Northern Provincial Council had recently called for a UN- backed investigation into the mass grave in Mannar, but the government has refused to consider such a request. Meanwhile the police are also investigating another mass grave in Central Sri Lanka where over 150 skeletal remains and bones had been unearthed last year. The mass grave in Matale was discovered when construction workers began digging the ground.