WASHINGTON — A new round of contracts has been awarded to build prototypes for a wall along the border with Mexico, the Department of Homeland Security announced on Thursday.

Two of the companies selected, Caddell Construction Company of Montgomery, Ala., and W. G. Yates & Sons Construction Company of Philadelphia, Miss., were also among firms awarded contracts last week to build concrete wall prototypes in the San Diego area.

The other companies chosen to build the wall prototypes are KWR Construction Inc. of Sierra Vista, Ariz., and ELTA North America Inc. of Annapolis Junction, Md.

The new wall prototypes will be 18 to 30 feet high and made of materials other than concrete, according to documents from Customs and Border Protection, an agency within the Department of Homeland Security. The agency did not say what those materials include.