ScienceDaily (Feb. 16, 2011) — Geologists drilling an exploratory geothermal well in 2009 in the Krafla volcano in Iceland encountered a problem they were simply unprepared for: magma (molten rock or lava underground) which flowed unexpectedly into the well at 2.1 kilometers (6,900 ft) depth, forcing the researchers to terminate the drilling.
http://www.sciencedaily.com/releases/2011/02/110216123545.htm