A recent study from the U.S. Geological Survey says the largest recorded earthquake in Kansas history was likely the result of waste water injected into the ground by one or two nearby wells.

The 4.9 magnitude earthquake happened in November 2014 about 40 miles southwest of Wichita.

The report, which will be published in Seismological Research Letters in November, shows scientists believe the earthquake was caused by waste-water injection for several reasons, including that there hadn’t previously been similar earthquakes in the area and the earthquake activity started after the amount of water injected in the wells increased.

One of the two wells operated by SandRidge Energy is still injecting water at the same level as when the earthquake occurred.

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Associated Press information from: The Wichita Eagle