More than $50,000 in reward money is being offered for information leading to the person believed to have killed dozens of protected wild burros in California’s Mojave Desert.

The reward rose to that amount Monday after an anonymous $32,000 donation to the Humane Society’s burro protection initiative.

Some 42 burros with gunshot wounds have been found along a 60-mile stretch of I-15 in the Mojave Desert since May. I-15 connects Los Angeles and Las Vegas.

FEDS OFFER $1,000 TO PEOPLE WILLING TO ADOPT AN UNTRAINED WILD HORSE OR BURRO

“Wild horses and burros are an iconic part of the American West, and part of our national heritage," said William Perry Pendley, the deputy director of the federal Bureau of Land Management (BLM), last week. "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."

Wild burros have been protected under a 1971 federal law. Violators would face a $2,000 fine and a year in jail.

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BLM law enforcement was leading the investigation into the illegal killings, in coordination with the San Bernardino County Sheriff’s Department, California Highway Patrol and the California Department of Fish and Wildlife.

“The persons who shot these innocent and beloved burros deserve to be brought to justice,” said Suzanne Roy, Executive Director of the American Wild Horse Campaign.

The Associated Press contributed to this report.