Eight prototype designs of President Donald Trump’s proposed wall along the U.S.-Mexico border will be demolished in San Diego, U.S. Customs and Border Protection confirmed Friday.

The border-security agency has not released details about its timeline for the demolition, but construction crews have begun work in the area to replace wire-mesh secondary fencing with taller, 30-foot-tall bollards.

Questions over the future of the eight structures — four made of solid concrete and four of mixed materials — had been unclear.

CBP had decided to keep the prototypes, which Trump visited in March, at the eastern outskirts of San Diego, just dozens of feet from the older, corrugated metal barrier that separates that city from a working-class neighborhood in Tijuana.

After Trump’s high-profile visit to the area last year, the structures became the most identifiable and tangible symbol of the president’s oft-repeated campaign promise to build a wall along the U.S.-Mexico border.

Since taking office, Trump has abandoned his idea of build a solid concrete barrier along the entire length of the border, and now wants see-though metal slats in certain areas.

Despite his claim that wall construction has already started, most of the barrier projects completed under his presidency have been replacement projects.

The demolition of the prototypes would mark the end of a sometimes-confusing $5 million process to solicit input and designs from the private sector to build additional barriers along the U.S.-Mexico border.

Soon after Trump took office, he directed Customs and Border Protection to begin work on construction of the wall. As part of that effort, the agency put out several requests for proposals to build eight 30-foot structures. Four would be made of solid concrete designs, while the other four would be made of «alternate materials.»

More than 600 companies expressed interest, but the agency eventually awarded contracts to six of them, worth an estimated $3 million. Construction crews began work on the prototypes in September 2017.

A month later, engineers began a series of military-grade testing to assess how well the designs would stand to scaling over, under, and through the structures.

Customs and Border Protection has not released details of the testing. But a Government Accountability Report published in July 2018 disclosed that the prototypes were riddled with design and engineering deficiencies that would make it hard to replicate them in other parts of the border.

Border officials said the solicitation process to build the eight prototypes was not intended to select a single winner, but to find design elements that worked and incorporate them into designs for future construction projects along the border.

Those efforts have been hindered by language that Democratic lawmakers attached to spending bills in the past two years, which limits Customs and Border Protection to using designs already in place.

One exception has been height. The government requested that all prototypes measure about 30 feet tall, while newer existing barriers measure between 18-feet-to-22-feet in height.

Since the completion of the prototypes, most of the replacement projects that have been completed or are underway use steel slats measuring 30 feet in height.