Federal authorities have yet to track down the person or people responsible for the escalating amount of deaths of wild burros in California's Mojave Desert. But they are hoping a $58,000 reward for information may help track them down.

Forty-two wild burros have been found illegally shot dead in northeast San Bernardino county since May. Activists and donors are now doubling down in their efforts to solve the crime.

The original reward was $10,000 but, thanks to new donations from conservation and animal welfare organizations, the reward has now risen to nearly $60,000, the U.S. Bureau of Land Management (BLM) in California said Wednesday.

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"Wild horses and burros are an iconic part of the American West and part of our national heritage," said William Perry Pendley, the BLM's Deputy Director for Policy and Program. "We will pursue every lead until we've arrested and prosecuted those responsible for these cruel, savage deaths and we welcome the public's help to bring the perpetrator or perpetrators to justice."

Thanks to substantial new pledges from several conservation and animal welfare organizations, the reward for information leading to the arrest and conviction of those responsible for the deaths of 42 #wildburros in California has risen to almost $60,000. https://t.co/fdZsBPqqfd pic.twitter.com/iKiOFlUhvA — Bureau of Land Management California (@BLMca) August 28, 2019

Burros are federally protected under the Wild Free-Roaming Horses and Burros Act of 1971. Anyone found guilty of capturing, branding, harassing or killing wild, free-roaming horses or burros could face a fine and jail time.

The total list of groups who have pledged money for the reward are:

"The murders of the Mojave Desert Burros must be punished to the fullest extent of the law," the Platero Project said in a statement. "Burros have been forgotten and underrepresented in the equine rights conversations. Burros must be given a prominent voice and enhanced status and protection on the range."

The Platero Project is a Humane Society initiative focused on the conservation of wild burros and mustangs.

"The senseless slaying of these wild burros is deeply disturbing, and anyone who is capable of this level of violence must be held accountable," said CEO and president of the Humane Society of the United States Kitty Block.