"The unauthorized placement of those containers constitutes a violation of federal law and is a trespass against the United States," Jacklynn Gould, a regional director for the U.S. Bureau of Reclamation, told Arizona Homeland Security Director Tim Roemer and Arizona Division of Emergency Management Director Allen Clark in the missive.

"That trespass is harming federal lands and resources and impeding Reclamation's ability to perform its mission."

Gould cited federal law that restricts public conduct on Bureau of Reclamation lands.

She asked officials to not place any additional shipping containers on federal lands or lands within the boundaries of Indian reservations, and said federal officials want to "discuss a way forward and requests your cooperation in the removal of the containers."