HENNESSEY, Okla. — After a series of small to moderate earthquakes in central Oklahoma, two companies are being told to reduce the amount of wastewater they inject into the ground.

About a dozen quakes have struck just south of Hennessey, about 45 miles (72 kilometers) northwest of Oklahoma City since Oct. 31, the largest being a magnitude 4.1.

There are no reports of injury or severe damage.

Oklahoma Corporation Commission spokesman Matt Skinner says Choate Disposal Service and Chaparral Energy were told to reduce their injection of wastewater in the area.

Thousands of quakes have struck Oklahoma in recent years, many linked to the underground injection of wastewater from oil and natural gas production. Several oil and gas producers have been directed to close some wells and reduce injection volumes in others.