Hundreds of red-winged blackbirds were found dead last week in a farming area near Bridgeton in South Jersey.
The Cumberland County Health Department and the New Jersey Departments of Agriculture and Environmental Protection are looking into whether toxins killed the birds.
DEP spokesman Lawrence Hajna said his agency is running tests, but has not come to a conclusion on the cause of death.
“Sort of a basic examination of stomach contents. And then there’s also more detailed tests of cellular structure in the birds themselves,” he said. “Those are more complicated, and we haven’t received those results back yet.”
A similar die-off occurred in the same county in 2012. In that case a legally applied pesticide to keep blackbirds out of the fields proved to be the culprit.
“Two-hundred, 300 birds may sounds like a lot,” Hajna said. “But it’s really not a lot when you consider the vast numbers of various species of blackbirds that are frequenting our rural areas, and even our urban areas, at this time of year.
Authorities said there is no threat to residents at this time.