Tens of thousands of dead fish have washed ashore along the Delaware Bay in southern New Jersey.

State environmental and wildlife officials say it’s not yet clear what killed the fish, which appear to exclusively small menhaden, also known as peanut bunker. But area residents are concerned:

“We’ll wait awhile until we go back into the water… until we know what’s going on.”

The wash-up, discovered Wednesday morning, encompassed a large stretch of the shoreline just north of Cape May. The heaviest amounts were in an area of Middle Township known as Pierce’s Point.

Locals didn’t know what to make of the discovery:

“It looked like white foam all over the place and so then I looked at it and thought, ‘Oh my God, they’re fish.’”

“It was really stinky and disgusting.”

New Jersey’s Bureau of Marine Water Monitoring reviewed results of water samples taken Wednesday by federal environmental officials and found no indication of toxic phytoplankton species, such as red tide.

State officials also are analyzing oxygen levels in the water.