This story will be updated as information becomes available.

Late on Thursday, the U.S. Department of Homeland Security's Customs and Border Protection (CBP) announced the names of four contractors that have been selected to construct "other materials"—any material of choice other than concrete—borderwall prototypes for a U.S.–Mexico borderwall. The companies are Montgomery, Ala.–based Caddell Construction Co.; Sierra Vista, Ariz.–based KWR Construction; Annapolis Junction, Md.–based Elta North America; and Philadelphia, Miss.–based W. G. Yates & Sons Construction Co. Both Caddell Construction Co. and W. G. Yates & Sons were also selected by CPB to build concrete borderwall prototypes last week.

Like the concrete prototypes, the alternate material borderwall prototypes will be between 18 and 30 feet tall, will be designed to deter illegal crossing across the U.S.–Mexico border. Additionally, the prototypes "will provide an innovative perspective in the application of new materials which will allow CBP to evaluate the potential for new wall and barrier designs to complement the current wall and barrier used along the Southwest border," according to the press release. The CBP estimates that the prototypes will be completed in the fall near to where the concrete prototypes are constructed in the San Diego area. Officials plan to meet with each vendor to determine specific timelines.

No specific materials for the prototypes have been named, and selections are at the vendors' discretion.