Bureau director Bob Abbey said: "The BLM is very serious about enforcing the 1971 law protecting wild horses on the range.
"The act very clearly states that it is a federal crime for any person to maliciously cause the death of any wild horse. BLM law enforcement is working closely with authorities in Washoe County to gather evidence and we are hopeful this reward will result in information leading us to the perpetrators of this crime."
On December 5, 2009, a helicopter crew conducting a wild horse gather saw five mustang carcasses in one area and a sixth dead mustang about a half mile away from the others.
Bureau officials from the Surprise Field Office in Cedarville, California, recognised the dead mustangs as belonging to a herd of horses known to roam the Buckhorn Herd Management Area.
Persons providing information may choose to remain anonymous. Individuals with information about this incident are encouraged to contact bureau Special Agent William Taylor.