Another earthquake hits Oklahoma as concern rises over wastewater injection

4.2 magnitude quake is among more than 800 in the state in 2015, and many are occurring in areas where wells pump byproducts of oil and gas production

A 4.2 magnitude earthquake struck north Oklahoma City early on New Year's Day, the latest in a series of temblors in the area in recent days that has prompted state regulators to call for more restrictions on oil and gas operators.

No injuries and only minor damage were reported with the quake, which struck at 5.39am on Friday near Edmond, about 16 miles north-east of Oklahoma City, according to the US Geological Survey.