The Environmental Protection Agency (EPA) said it will order some wastewater disposal wells to be shut in following an earthquake in Oklahoma.
It comes after a 5.6 magnitude earthquake on Saturday.
The quake is believed to be one of the strongest ever recorded to hit the state and has prompted the oil and gas regulator, the Oklahoma Corporation Commission, to call for 37 disposal wells to be shut in a 725-square-mile area around Pawnee.
The EPA has also been asked to help shut disposal wells in a 211 square-mile area of Osage County because the Commission lack focus there.