Sri Lankan authorities are investigating a new mass grave found in an area in the north of the country which was once under rebel control, the police said on Sunday. Police spokesman Ajith Rohana said that excavation work was carried out at the mass grave in Mannar in the presence of a Magistrate and other officials. The grave site which was stumbled upon this month had at least 10 human skeletal remains buried inside. Following its discovery an investigation was launched and forensic examinations were carried out. The police spokesman said that there is a suspicion that the grave was used by the Tamil Tiger rebels during the war to bury civilians and soldiers killed by the rebels. The Tamil Tigers controlled most parts of the north including parts of Mannar for nearly 30 years before the military launched an operation to regain control over those areas. Following a bitter and bloody war in which thousands were killed the rebels were defeated in May 2009 ending with the death of the rebel leader himself. However since 2009 allegations of war crimes committed by the army and rebels have surfaced and there are now calls for an international investigation on Sri Lanka. The discovery of the grave in Mannar comes even as Sri Lanka investigates another mass grave found in Matale, in central Sri Lanka. Over 150 skeletal remains and human bones had been unearthed from the mass grave in Matale late last year. Forensics had determined that the remains were of those killed sometime in the late 1980s.