A former employee says wild horses on a South Dakota ranch are dying of starvation and other causes.

The Rapid City Journal reports that the Dewey County sheriff is investigating the situation. Former International Society for the Protection of Mustangs and Burros employee Colleen Burns estimates over 30 horses have died since June.

Burns says she was fired Thursday after publicizing her allegations about conditions at the north-central South Dakota ranch. Karen Sussman, president and longtime leader of the society, says Burns is a “disgruntled employee.”

Burns says insufficient grass and financial troubles making the society unable to buy enough hay have led to the deaths. Dewey County Sheriff Les Mayer says he ordered Sussman to feed the horses each day or risk citation or arrest.