YOUNGSTOWN, Ohio, Jan. 2 (UPI) -- Ohio officials say they have shut down four fluid-injection wells after a series of small earthquakes in and around Youngstown.
The move came after the latest and strongest of a series of recent earthquakes, a 4.0-magnitude temblor Saturday with its epicenter 5 miles northwest of Youngstown and 55 miles east-southeast of Cleveland, CNN reported.
The fluid-injection wells are used to dispose of brine wastes from gas and oil drilling by pumping them into rock formations deep underground. The waste fluid is a byproduct of hydraulic fracturing, or fracking, in which water, sand and chemicals are injected deep into the ground at high pressure to crack shale and allow gas or oil to flow.
Saturday's quake, which struck 1.4 miles deep, had 40 times more energy than any of the 10 that had occurred in the area in 2011, officials said.
The wells will remain closed as officials investigate a possible link between the earthquakes and the fluid-injection wells, said Andy Ware, deputy director of Ohio's natural resources department.
"They will [not open] until we are satisfied that the process can be safely resumed," Ware said.