For the second time in two weeks, fish have been found dead in an eastern Kentucky creek, and state regulators aren’t sure what factors are to blame for the fish kill.

This time, hundreds of dead fish were found in Catrons Creek, in Harlan County. The dead fish range from more than a foot long to minnows.

But no one knows what caused the fish kill yet. People living near the creek reported seeing black water, and the culprit could be some kind of discharge of chemicals upstream from a coal mine or other industry.

“It’s looking like there’s something discharging, some kind of contaminant in the water,” Division of Fish and Wildlife officer Steve Combs said. “We don’t have any evidence of that, because by the time people call us and we get people there to take samples, a lot of time it’s flushed out.”

There was also no sign of a toxic algae bloom, which can be caused by excess nutrients in the water.

Now, regulators are waiting for the results of water tests to try to determine what’s to blame for the fish kill. They’ve tested for volatile organic compounds, heavy metals, dissolved oxygen and pH, and should have the results in about two weeks.