Somewhere within the twisted metal of Sudan\'s damaged Heglig petroleum complex may lie the evidence to prove who caused the destruction during the 10-day occupation of the region by South Sudanese troops last month. The United Nations has called for an impartial investigation into what happened at Heglig during the border war which sparked international alarm. Sudan and South Sudan have blamed each other for the extensive damage to the export pipeline and central processing facility serving the north\'s main oil field. Sudanese officials said it produced roughly half the national production before South Sudanese forces moved in on April 10, disputing the north\'s claim to the area. During the occupation South Sudan\'s army alleged the north bombed the Heglig area \"indiscriminately,\" and that an air raid struck the processing facility, setting it ablaze. But the north blamed southern troops and called for compensation. An African diplomat taken on a government-run tour a few days after Heglig\'s \"liberation\" said the damage did not appear to have been caused by aerial bombing. He said an explosion under the facility\'s power station had left depressions in the ground and the metal roofing was blown out -- damage inconsistent with an air strike. The diplomat, who declined to be identified, said he could still detect the smell of explosives and felt South Sudan was responsible. \"My sense is that, I can\'t see how Sudan would\'ve self-inflicted that kind of thing on themselves,\" the diplomat said. \"It was well thought out, well executed... just enough to cause disablement, at least for a while.\" But he said some observers in Khartoum disagree, believing that either side could have done it. \"There are some who say that,\" he added. A source close to the oil industry also felt the South was behind the damage because it could not have been caused by aerial bombing. Sudan announced last week that it had resumed pumping oil from the partially-repaired Heglig facility but the source said it would take months to resume full production. An international economist estimated that Sudan\'s oil revenues shrank by more than $700 million after Heglig was damaged. South Sudan separated last July with about 75 percent of the former united Sudan\'s oil production, leaving Khartoum struggling for revenue and hard currency. Juba still depended on the north\'s pipeline and Red Sea port to export its crude, which it said provided 98 percent of its earnings,. But a protracted dispute over fees for use of that infrastructure was at the heart of tensions which brought the two countries to the brink of all-out war and led South Sudan in January to shut its oil production. \"It seems quite plausible to me that South Sudan did it,\" an international analyst said of the Heglig damage. Despite Sudan\'s claims to have driven the South Sudanese troops from Heglig by force, the analyst and the diplomat said there had not been heavy fighting in Heglig itself, supporting the argument that Sudan wanted to preserve the oil facility. \"You would\'ve seen artillery shells quite extensively... pock marks, and (battle) damage\" if there had been intense combat, the diplomat said. Corpses that were scattered about, \"may have been of a show nature,\" he added. Sudan did not allow journalists into the Heglig area during clashes with the South, and granted them only brief access on government-escorted tours after South Sudan said it had withdrawn. \"They did not want them to witness this damage,\" said South Sudan\'s military spokesman Philip Aguer. \"Whatever story Khartoum is giving, it\'s a fabrication. It is their own bombing. It is their own destruction,\" he said. \"Khartoum is a country based on denial.\" Magdi El Gizouli, a fellow at the Rift Valley Institute, a non-profit research group, said that because it was a war zone, \"I think both parties contributed to the damage\". Under a May 2 UN Security Council resolution, the two countries are to cease hostilities and resume by next Wednesday negotiations on unresolved issues including oil. The resolution also calls for \"an impartial fact-finding effort to assess the losses and economic and humanitarian damage, including to oil facilities and other key infrastructure, in and around Heglig.\" South Sudan is ready to comply with \"all the articles\" in the UN resolution, Minister for Cabinet Affairs Deng Alor said. The African diplomat said the UN call for fact-finding is significant because in a climate of war rhetoric, \"the first victim is truth.\"