Environmental regulators in Michigan have approved new rules for energy companies that produce natural gas by cracking open underground rock formations.
The regulations announced Wednesday by the Michigan Department of Environmental Quality would require the companies to meet additional requirements for public disclosure and protecting water resources.
The new rules involve the gas extraction method known as hydraulic fracturing, or "fracking." It pumps sand, water and chemicals under high pressure into underground wells to open fissures in rock through which the gas can escape and be extracted.
The process has drawn criticism in Texas and other states, where opponents say it contaminates the soil and ground and surface waters.
The DEQ says the method has been used on nearly 12,000 wells around Michigan since the 1960s without damaging the environment.