Customs and Border Protection shared the first photos of one concrete border wall prototype being built at the U.S.-Mexico border in San Diego, Calif.

The cement structure will be up to 30 feet tall and is one of four concrete prototypes being constructed at various points of the southwestern border.

Last month, CBP's parent organization, the Department of Homeland Security, awarded six companies up to $2.4 billion total to build the eight prototypes.

The companies were selected from hundreds that submitted proposals earlier this year on how to create border barriers.

Caddell Construction Company, Fisher Sand & Gravel Company, Texas Sterling Construction Company, and W.G. Yates and Sons Construction Company will each receive up to $300 million to build a solid concrete wall prototype.

Caddell and Yates, as well as KWR Construction, Inc. and ELTA North America Inc. will also be given up to $300 million each to build "alternate materials border wall prototypes," according to CBP.

The project is being funded with "reprogrammed money" taken from within CBP, and is not part of the $1.6 billion border wall funding the House of Representatives approved in June, DHS told the Washington Examiner. The $1.6 billion in border wall funding has yet to pass in the Senate, and may not make it out of Congress for months, if it does at all.

All of the prototype projects will be carried out on the border and are expected to start this fall, but the non-concrete walls will conclude years before the concrete projects. Each of the eight prototypes will be between 18 and 30 feet tall, and address specific issues Border Patrol agents deal with in certain regions, such as community, geography, and wildlife concerns.

Homeland Security chose to have a number of wall types built so they can see how border operations are carried out with different barriers.

Trump signed the Border Security and Immigration Enforcement Improvements executive order five days after becoming president. The action called for DHS to "take steps to immediately plan, design and construct a physical wall along the southern border, using appropriate materials and technology to most effectively achieve complete operational control of the southern border."

CBP put out two requests for wall design proposals on March 17.