An unknown illness is killing bald eagles in Utah. So far, 16 have died. 

The ailment’s symptoms begin with overall weakness, progressing to paralysis in the legs, tremors and seizures, and finally death. Scientists are rigorously seeking an answer to what’s causing the sickness to prevent more from dying. Thus far, there have been no breakthroughs as to the origin of the disease.

December has been a bad month for the magnificent national bird and national animal of the US. Earlier this month, President Obama extended leasing terms for windmill farms up to thirty years, greatly contributing to the slaughter of the eagles. The beleaguered bald eagle was placed on the endangered species list in 1967 and was only removed from the list in 2007. 

Wildlife experts are recommending that people contact the Division of Wildlife Resources right away if they find a bald eagle in distress. DaLyn Erickson-Marthaler of the Wildlife Rehabilitation Center of Northern Utah says that the organization has not ruled out any possible cause yet, but it looks unlikely that the birds have been intentionally poisoned. 

“I couldn’t even begin (to speculate) what’s wrong with them yet. If we start focusing on one thing right now, we could miss something else entirely,” DaLyn told NBC News.