Agriculture officials have quarantined 28 beef cattle on a Pennsylvania farm after wastewater from a nearby gas well leaked into a field and came in contact with the animals.

The state Department of Agriculture said the action was its first livestock quarantine related to pollution from natural gas drilling. Although the quarantine was ordered in May, it was announced Thursday.

Carol Johnson, who along with her husband owns the farm in north-central Pennsylvania, said she noticed in early May that fluids pooling in her pasture had killed the grass. She immediately notified the well owner, East Resources Inc.

"You could smell it. The grass was dying," she said. "Something was leaking besides ground water."

The Johnsons' farm sits atop the Marcellus Shale, a layer of rock that lies under swaths of West Virginia, Pennsylvania, New York and Ohio. As ProPublica has reported, reports have proliferated of groundwater pollution, spills and other impacts of hydraulic fracturing, a drilling technique that injects massive amounts of water, sand and chemicals underground to break up the formations that hold the gas.

In the Johnsons' case, a mixture of fresh water and wastewater that had been injected into the well leaked from an impoundment pit on the farm, the state Department of Environmental Protection (DEP) said. Tests performed for East Resources Inc., found hazardous chemicals and heavy metals, including chloride, barium and strontium. East did not dispute that a leak had occurred.

It's unclear whether the Johnsons' animals drank any of the wastewater. The quarantine was put in place to ensure the animals did not go to market with contamination.

An inspection conducted May 3 by the DEP found two seeps from the impoundment. According to the inspection report, an East Resources employee said a contractor had inspected twice in April and he was unsure why the leak wasn't detected earlier.

The DEP inspector issued four violations for the leak and resulting pollution. One cited East's failure to notify the department of the pollution, saying the agency learned about it from the Johnsons' daughter.

State records show that the well, also on the Johnsons' property, was issued five violations by DEP in January, including one labeled "Improperly lined pit." A February inspection found no violations.

Stephen Rhoads, director of external affairs for East Resources, said the January violations were for spilled drilling mud and were unrelated to the subsequent pit leak.

East Resources said tests of the leaked fluid did not show unhealthy levels of any contaminants and that the quarantine was unnecessary. Rhoads said hydraulic fracturing, called fracking for short, had begun April 2 and that wastewater wasn't impounded until a week later.

Upon being notified May 2, Rhoads said, the company immediately fenced off the Johnsons' pasture and began to empty the impoundment and remove all contaminated soil. The well has since been shut down.

The incident isn't the first report of farm animals being affected by fracking. As we reported more than a year ago, 16 cattle died in Louisiana after drinking a mysterious fluid next to a drilling rig.

The Johnsons' cows have fared better so far.

"They're happy, contented, fat," Johnson said.