The United States Fish and Wildlife Service is trying to determine who or what killed the 13 bald eagles that were recently found dead in a Maryland community.

According to a news release from the service, a citizen on Saturday discovered some of the deceased birds in a field in Federalsburg, a town in the center of the Delmarva peninsula.

Investigators searched the area and ultimately found 13 bald eagle carcasses, the service said.

The iconic eagles are the official bird of the United States and appear on the country’s Great Seal and currency. While the eagles were moved off the endangered species list in 2007, the service says the birds are still protected under federal laws that criminalize killing or wounding them.

Anyone found guilty of violating the Bald and Gold Eagle Protection Act can be fined up to $100,000 and sentenced to a year in prison, according to the service, which is teaming up with a variety of animal protection groups to offer a reward for information that leads to a conviction.

The total reward stood at $25,000 following a $15,000 pledge from the Center for Biological Diversity, the nonprofit organization said in a news release. The center added the 13 bald eagle deaths are the most that Maryland has experienced in any one incident in more than 30 years.

“For many Americans the bald eagle represents freedom and strength,” Catherine Kilduff, an attorney for the Center for Biological Diversity, said in a statement. “The unthinkable death of 13 birds at once stands in stark contrast to the ideals this majestic wild animal personifies.”

Authorities believe the birds might have been poisoned, according to the center.

“If they were poisoned or shot, the heartbreaking deaths of these 13 bald eagles is a crime,” Kilduff said in a statement. “Those responsible need to be caught and prosecuted.”