(CNN) Four women who left food and water for migrants in the Arizona desert have been sentenced and fined for entering a national wildlife refuge without a permit.

The women were sentenced Friday to 15 months of unsupervised probation, fined $250 each and banned from the Cabeza Prieta National Wildlife Refuge in Ajo for the duration of their probation.

Zaachila Isabel Orozco-McCormick, Natalie Renee Hoffman, Oona Meagan Holcomb and Madeline Abbe Huse are volunteers with the organization No More Deaths/No Más Muertes, a group that says it's "dedicated to stepping up efforts to stop the deaths of migrants in the desert."

In the summer of 2017, No More Deaths said, the women left jugs of water and food in the desert of the wildlife refuge, which is near the US border with Mexico.

That summer was one of the hottest on record in Arizona, the statement said, and the women left the supplies "in the hopes of staving off death by dehydration for people walking in the desert."

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