(CNN) Four aid volunteers are facing prison time after leaving food and water inside an Arizona national wildlife refuge where undocumented migrants have died trying to enter the United States.

The volunteers, who are part of the No More Deaths ministry of the Unitarian Universalist Church of Tucson, could be sentenced to up to six months in prison and fined up to $500 after they were convicted Friday by Federal Magistrate Bernardo Velasco.

The volunteers -- Natalie Hoffman, Oona Holcomb, Madeline Huse, and Zaachila Orozco -- were charged with entering a national wildlife refuge without a permit and abandonment of property, according to a statement from the aid group.

Five other No More Deaths volunteers face charges for "efforts to place life-saving food and water" inside the Cabeza Prieta National Wildlife Refuge , the aid group said. Those volunteers will have trials in February and March.

Cabeza Prieta is Arizona's largest wilderness area, spanning 803,418 acres of isolated and rugged landscape of the Sonoran Desert. A joint investigation was launched by US and Mexican authorities in 2001 after at least 14 migrants died in a single incident after crossing the border in the refuge. They probably were abandoned in the desert by people smugglers, authorities said at the time.

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