Jakarta – Indonesia's state oil and gas company Pertamina said Saturday it had shut off gas lines near a "mud volcano" for safety reasons, as railways and roads were again flooded with toxic sludge.

"The ground near the pipes has subsided – thus the mud surface has almost reached the gas pipes," company spokesman Toharso said in a statement, announcing that the pipes had been shut down from 5:00 pm Friday.

The steaming crater, located near Indonesia's second-largest city of Surabaya in East Java, first began spewing mud in May after exploratory gas drilling at the site by a local firm, PT Lapindo Brantas.

The sludge has inundated some 600 hectares (1,500 acres), including many homes and factories, leaving thousands of people homeless and jobless. Indonesian experts are trying to slow the flow by dropping chains of heavy concrete balls into the funnel, a bold plan some say will not work.

The mud also threatens to swamp a key railway, which is to be rerouted away from the danger zone. One of the main tracks – still being used by trains passing through the area – is now covered in three centimeters (two inches) of mud, police said Saturday.

Late Friday, workers frantically piled sandbags along the main road connecting Surabaya to the city of Porong to hold back the oozing sludge, but traffic had to be diverted on Saturday, causing major disruptions.

"Mud flooding on the tracks and Porong road is worse than yesterday and traffic has to be diverted to an alternative road," officer Andi Yudiyanto said on ElShinta radio.

East Java governor Imam Utomo visited the affected area on Saturday and ordered redoubled efforts to reopen the road and clear the railway line.

National Planning Minister Paskah Suzetta has said the cost of managing a series of natural disasters like the "mud volcano" is likely to send Indonesia's budget deficit spiralling upwards.