Arizona Gov. Doug Ducey said Thursday that the "Border Barrier Mission is working" after the state refused to remove double-stacked shipping containers along gaps in the southern border.  

"Arizona is protecting its citizens," Ducey tweeted on Thursday afternoon. "Why the federal government won’t is beyond belief." 

Ducey announced in August that Arizona had filled nearly 4,000 feet of gaps in the border with shipping containers that were welded shut and topped with 4 feet of razor wire. 

Arizona shipping containers

Construction to place these shipping containers in gaps in the border wall began on Aug. 12, 2022, in Yuma, Arizona.  (Ashley Soriano/Fox News)

Arizona border wall

In this aerial view, Cuban immigrants seeking asylum in the United States await transport by the U.S. Customs and Border Protection after they crossed into Arizona from Mexico on Sept. 27, 2022, in Yuma, Arizona.  (John Moore/Getty Images)

The Department of Interior’s Bureau of Reclamation wrote in a letter to Ducey's administration last week that the "unauthorized placement of those containers constitutes a violation of federal law" due to their proximity to the Morelos Dam and land that is part of the Cocopah Indian Tribe’s West Reservation. 

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Allen Clark, director of Arizona’s Department of Emergency and Military Affairs, fired back this week, writing that the state "cannot rely on the federal government to ensure its security."

"The myriad of federal agencies that claim jurisdiction on the southern border but do nothing to prevent the public nuisance caused by illegal immigration and criminal activity that exploits the open border is quite frustrating to those that live, work and recreate on that border and in our state," Clark wrote in a letter to the Bureau of Reclamation. 

Arizona border shipping containers

Shipping containers fill gaps in the border wall in Yuma, Arizona.  (John Moore/Getty Images)

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The federal government told Arizona in December 2021 that it would soon start filling in gaps in the border wall, but the state felt compelled to take matters into its own hands after months of inaction, according to Clark. 

There have been more than 2.1 million migrant encounters at the southern border so far this fiscal year, including more than 284,000 in the Yuma sector and more than 230,000 in the Tucson sector, which comprise Arizona, according to Customs and Border Protection data. 

Fox News' Adam Shaw contributed to this report.