But the team led by Richard Davies, a professor at the University of Durham in northeastern England, believes drilling at a depth of nearly 3km ruptured a highly pressurised pocket of hot gas and water which created fissures in a bed of porous limestone, causing the volcano to spew out mud.
"It is standard industry procedure that this kind of drilling requires the use of steel casing to support the borehole, to protect against the pressure of fluids such as water, oil or gas," Davies said.
"In the case of Lusi, pressured limestone rock containing water … was drilled while the lower part of the borehole was exposed and not protected by casing.
"As a result, rocks fractured and a mix of mud and water worked its way to the surface.
Our research brings us to the conclusion that the incident was most probably the result of drilling."
The scientists said the flow could last for months or years, causing the earth to sink.
An area of at least 10 sq km will be uninhabitable for years, and over 11,000 people will be permanently displaced.
Davies said the case in Indonesia was similar to one that happened offshore of Brunei in 1979.
"Just as is most probably the case with Lusi, the Brunei event was caused by drilling and it took an international oil company almost 30 years and 20 relief wells and monitoring before the eruption stopped," he said.
Scientists say the mudflow could last
months or even years [GALLO/GETTY
But more testing is needed to accurately forecast the impact on the local population, the scientists wrote.
The report was not based on firsthand field work, but data from two UN technical missions, the US Geological Survey, satellite images and dozens of previous studies on volcanic mud eruptions.
Since May, around 126,000 cubic metres of sediment - equal to around 50 Olympic swimming pools - has gushed from the site every day.
About 11,000 people have been forced from their homes while four villages and 25 factories have been consumed by a 10-metre layer of smelly gunk.
In November, a natural gas pipeline cracked under the weight of a dam built to channel the mud to the sea, triggering a powerful explosion that killed 13 people and injured a dozen others.
The government, which has purchased flooded land from victims, has said it will seek an initial $420 m in damages from Lapindo, including $276 m paid to the victims, by March 2007.
Aburizal and his brothers own a 60 per cent stake in PT Energi Mega Persada Tbk, Lapindo's parent company.
The Bakrie Group has twice tried to sell off the Lapindo subsidiary since the disaster, but Aburizal denies it was an attempt to dodge its corporate responsibility.
"It is truly a natural disaster," he told reporters last week. "It has nothing to do with the Lapindo drill."