BALTIMORE -- More bad news for bald eagles.

Police are now investigating the deaths of five bald eagles in Delaware, CBS Baltimore reported.

This just weeks after more than a dozen were found dead in Maryland.

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This time a man discovered an eagle was sick in Delaware and called the Department of Natural Resources.

"At the time, a single bird didn't raise any red flags," said Sgt. John McDerby, DNREC Division of Fish & Wildlife Natural Resources Police. "Little bit later that morning, another officer received a call that there were eight eagles on the ground and some of them seemed to be in distress."

Five of the eight eagles have now died. Three are being treated at a rescue facility.

This comes after 13 bald eagles were found last month, just 30 miles away, near Federalsburg in Caroline County, Maryland, CBS Baltimore reported.

Police say those eagles may have ingested some kind of poison.

"It was really devastating to our officers," said Sgt. McDerby. "Here in the business of protecting wildlife to see 13 dead eagles in a field is pretty hard to take.I think it's too early in an investigation to try and make any kind of guess if things are related. At this time we are investigating it as a separate incident."

It will take a few days for test results to determine how the bald eagles died.

U.S Fish and Wildlife is now offering a $25,000 reward to anyone who can lead to the person or persons who killed the birds in Maryland.