GRAND RAPIDS, Mich. (WOOD) — Officials and local residents are searching for answers after multiple people noticed a creek in Michigan turn an eye-popping shade of green.

Photos from viewer Steven Littell on Monday afternoon showed bright green water in Plaster Creek near Cesar E. Chavez Avenue, which is on the border of Grand Rapids and Wyoming.

The City of Grand Rapids went to check it out Monday after receiving the complaint but when workers got there, they said the green was gone.

Nexstar’s WOOD-TV also went to check out the creek Tuesday, but did not see the green hue.

“My significant other and I were driving by, and she said, ‘Look at the creek.’ I stopped and it was fluorescent green. It was like almost glowing. So I got out and got a couple shots,” said Steven Littell, who sent the photos to WOOD. “Came back and checked on it for the next hour or so — it ran green for pretty close to an hour.”

“It worried me. I thought somebody was dumping something that shouldn’t have been dumped in there. It didn’t look right. This goes right to the Grand, right to Lake Michigan, so it worried me,” said Littell.

Jeff Johnston, a spokesperson with the Michigan Department of Environment, Great Lakes and Energy said staff has inspected the creek at the location Littell found the green color and found that it had already run clear.

“The color appears to have been from a dye test, likely performed near where the color was observed, and that material dissipates quickly,” said Johnston.

The Grand Rapids wastewater/stormwater maintenance superintendent agreed that it looks like the green dye that is used to determine where water is flowing.

But the city clarified that it wasn’t doing any tests Monday.

The mystery of the green water continues.