A mud volcano, which began erupting two years ago on the Indonesian island of Java, forcing thousands of people to flee their homes, could be on the verge of collapse, British scientists have found.

Many people believe gas drilling caused the phenomenon

The Lusi volcano has displaced 50,000 people, submerged homes, factories and schools and is flowing at a rate of more than 3.5 million cubic feet a day.

Despite efforts to halt the flow, including dropping giant concrete balls into the crater, the hot, noxious grey mud continues to spurt from the site in Sidoardjo, East Java.

Many believe gas drilling caused the phenomenon, which began two days after an earthquake in May, 2006. The government has ordered the drilling firm to pay compensation.

But research by Durham University and the Bandung Institute of Technology has found the volcano is collapsing and could subside to depths of more than 460 ft.

Inflammable gas had begun escaping from the ground, threatening those who have so far escaped the mud.