 Gas and hot mud started spewing from the well on May 28, when the drill penetrated a layer of liquid sediment.Attempts to pump concrete down the well did not stop the flow.While some scientists have speculated that the earthquake that struck Yogyakarta on May 27, the day before the well erupted, may have cracked the ground, creating potential pathways for the mud to reach the surface, others have suggested that the drilling procedure was faulty by not using a casing.