Villagers have built a meter-high (three-foot) wall of sand bags over an area of some 40 metres by 30 metres in an attempt to contain the flow.

It was the second mud flow since a gas drilling operation in Sidoarjo, East Java, led to a fountain of hot mud in August that has since submerged hundreds of hectares of land and villages and forced the evacuation of some 13,000 people.

"The mud contains a high level of nitrogen oxide and the gas coming out of the source also contains a high level of CH4, that is a light, odorless and colorless gas that is highly inflammable," said Heryo Dharma, the deputy head of the province's mining office.

He said the CH4, or methane gas, content was well above the safe level and that local authorities have banned any flame, including lit cigarettes, around the site.

"Since there are toxic and dangerous substances in area, we the local government have no authority to do anything but to report to the central government," Dharma told AFP.

He said he had been ordered to fly to Jakarta on Thursday to report to the energy and mineral resources ministry.

The mud, which had initially spurted from a small drilling hole, was now coming out from an area more than five meters across, he said, and could spurt up to a height of two meters.

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