Read the passage and answer the question: Nine years ago, a rice paddy in eastern Java suddenly began spewing steaming mud. Before long, it covered three square miles; roads, factories and homes disappeared under a tide of muck. Twenty lives were lost and nearly 40,000 people displaced, with damages topping $2.7 billion. The disaster, known as the Lusi mudflow, continues to have its impact till now. A mud volcano, Lusi expels water and clay rather than molten rock. Such eruptions occur around the world, but Lusi is the biggest and most damaging known. Scientists have debated the cause for years, and two intensely argued hypotheses have emerged: some believe an earthquake set off the disaster, others that the mudflow was caused by a company drilling for natural gas. Researchers largely relied on computer models and comparisons with other earthquakes and mud volcano eruptions. But recently scientists uncovered a previously overlooked set of gas readings collected at the drilling site by Lapindo Brantas, a natural gas and oil company, in the days before the mudflow began. In a report in the journal Nature Geoscience, the researchers said that the new data proves that the drilling by the company caused the disaster. — A synonym for 'expel' would be: