(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."

In addition to entering without a permit, the women were also accused of abandoning personal property, according to a statement by the Department of Justice. Hoffman was also convicted of operating a motor vehicle in the refuge.

According to the statement by No More Deaths, the judge presiding over the women's trial said in court: "I think it goes without saying: You need water in the desert, and without water you will die."

First Assistant US Attorney Elizabeth A. Strange commended the work of the United States Fish and Wildlife Service for its commitment to preserving the land.

"Our office will continue to review potential violations on federal lands on a case-by-case basis and bring charges, as appropriate," Strange said.

Last month, another group of No More Deaths members avoided prosecution, according to the organization. The group of four people faced the same charges, but agreed to receive civil infractions and a $250 fine in exchange for criminal charges being dropped, No More Death's said in the statement.

According to the organization, another member will go to trial in May for misdemeanor charges for actions in Cabeza and three felony charges for aid work in other places.