The US government on Thursday announced the names of four firms that will build concrete prototypes for the US-Mexico border wall and that were selected for the characteristics of the mock-ups that they propose to construct, although the wall itself will be designed to halt the illegal entry of undocumented migrants.

The companies are Caddell Construction of Montgomery, Alabama; Fisher Sand & Gravel of Tempe, Arizona; Sterling Construction, of Houston, Texas; and Yates & Sons Construction of Philadelphia, Mississippi, according to the announcement made by Customs and Border Protection officials at a press conference.

The firms will be in charge of building the prototypes for the wall along a stretch of the border in San Diego, California, and will have a budget of $20 million.

Acting CBP deputy commissioner Ronald Vitiello, said that the prototypes will be built one beside the other in the designated zone of San Diego and a team of officials will be tasked with determining their effectiveness in detaining the arrival of immigrants, both over and under the wall.

All the prototypes will measure 9 meters (30 feet) and will be between 5.5 and 9 meters (18-30 feet) high.

"We'll look at things like the aesthetics of it, how penetrable they are, how resistant they are to tampering and then scaling or anti-climb feature," Vitiello said.

Next, the government will "sit down with these companies and discuss timing," Vitiello said, noting that the discussions will be held "within a couple of weeks."

He also said that, in all, there will be between four and eight prototypes built in San Diego, and the government could announce additional names of companies selected to participate in the project during the coming week.

In addition, next week, the government will announce a decision on "other materials" designed to technologically augment monitoring capabilities along the wall.

Construction of the prototypes will begin in the fall, although initially the US government had announced that the first prototypes would be built in the summer.