A couple of major earthquakes in Oklahoma in recent weeks have raised concerns after years of a declining number of quakes and forced a state agency to shut down wastewater injection wells.

 A 5.1-magnitude quake last week was one of the strongest in years. Most scientists agree the quakes in Oklahoma are related to the high-pressure injection deep underground of wastewater left over from oil and natural gas production. After an uptick in quakes, regulators years ago placed new restrictions on disposal wells.

The Oklahoma Corporation Commission ordered all disposal wells within 10 miles of Prague in Lincoln County to shut down by Feb. 17. The area is the epicenter of the Feb. 3, 5.1-magnitude earthquake.

The quake would be tied as the fourth-strongest in Oklahoma history if seismologists maintain the rating.