Indonesian police have stopped a criminal investigation into whether drilling at a gas exploration well caused a devastating mud volcano in East Java because of a lack of evidence, police said on Friday, according to Reuters. The hot mud, which started erupting in May 2006 near Indonesia's second-biggest city of Surabaya, has destroyed homes, factories, and livelihoods. Some scientists have said that energy firm PT Lapindo Brantas' drilling for a gas exploration well set off the mud volcano, but Lapindo has denied it is to blame, saying the mud disaster was triggered by tectonic activity. "We officially stopped the investigation on Thursday because we could not find evidence that there is a correlation between the mud flow and the Banjar Panji well," East Java police spokeswoman Pudji Astuti said. She said the police had failed to find an expert or witness who could prove that the drilling was the cause of the mud flow. An international team of experts, led by Richard Davies of Britain's Durham University, had said last year it was almost certain that drilling for a gas exploration well, and not an earthquake, set off the volcano in East Java. The team had said records kept by Lapindo during the drilling of the gas exploration well showed an underground blowout that could have triggered the disaster. But Bambang Istadi, a geologist at Lapindo, said after the report that tectonic activity had caused an old escarpment to crack and become the channel for the mud to flow. Efforts so far to staunch the flow have failed and now the mud covers an area of about 800 hectares (1,977 acres) and has displaced nearly 60,000 people. The mud volcano has also been particularly embarrassing for the government of President Susilo Bambang Yudhoyono, since Lapindo is linked to the Bakrie Group, controlled by the family of Indonesian Chief Welfare Minister Aburizal Bakrie. All legal attempts to pin blame on anyone for the disaster have so far failed. In 2007, the South Jakarta Court dismissed a lawsuit by an environmental group, WALHI, and decided that the mud volcano was a natural phenomenon, not a man-made disaster. In a separate lawsuit, the Supreme Court in April also dismissed a law suit by a legal aid foundation, YLBHI, that the government has failed to protect the rights of its citizens in the mud case.