Work on "virtual fences" planned for Arizona's stretch of the U.S.-Mexican border has been brought to a halt.

The Interior Department has not granted the Homeland Security Department permission to use the land for constructing the surveillance towers that form the backbone of the virtual fences, said Barry Morrissey, spokesman for U.S. Customs and Border Protection in Washington, D.C.

Without authorization to use the land, no work could begin, which prompted agency officials to instruct the lead contractor on the project, Boeing Co., to suspend activities until further notice, Morrissey said.

No date has been set to resume work.