Michigan has cited an energy company for spilling 300 to 400 gallons of water and brine into the ground on the site of a fracking well in Kalkaska County.
The state Department of Environmental Quality this week issued a violation notice to Encana Oil and Gas Inc. for an incident July 15.
The spill was related to hydraulic fracturing, which releases natural gas trapped in deep underground rock formations.
Canada-based Encana was cleaning out the well hole to prepare for production testing. But water pumped back to the surface inadvertently leaked from a tank.
The state says there's no lasting environmental damage, and Encana quickly cleaned up the site.
No fine was issued.
An Encana spokeswoman said Friday soil samples are being tested, but the company's confident in the cleanup.