Officials in Arkansas are turning their attention now from the skies to the rivers as an estimated 100,000 fish turned up dead in the Arkansas River a little over 100 miles from Little Rock.

Experts suspect the culprit to be an unknown disease. Arkansas Game and Fish Commission employee Keith Stephens said that fish kills happen every year, but rarely with these kinds of numbers.

The fish kill happened near the town of Ozark, which is roughly 125 miles from Beebe, the town where 5,000 blackbirds rained from the sky on New Year’s Eve.

The dead fish were discovered by a tugboat operator on the Arkansas River, and officials collected some samples in order to discover what caused the mass death. According to Stephens, the dead fish covered about 20 miles of riverbank.

“The fish kill only affected one species of fish,” he said. “If it was from a pollutant, it would have affected all of the fish, not just drum fish.”

Stephens went on to say that the bird deaths were most likely stress related, and have absolutely no connection to the dead fish near Ozark.

Health officials are currently on site and are investigating further into the matter.