Screenshot, Donald Trump
Construction crews have already begun work on prototypes for President Donald Trump’s proposed border wall.

Reporters and social media users are getting their first glimpses of prototypes for President Donald Trump's border wall.

Reports about the border wall prototypes first came out late last month. Photos, videos and stories have since been making their way online.

Trump tweeted a video of the prototypes on Wednesday, sparking renewed interest:

The prototypes are being built in "a remote section of the San Diego borderlands,” according to an NPR report Thursday.

Four of them are made with reinforced concrete, while four others are being made with "other materials," The New York Times reported. One of them is topped with spikes.

The companies have until Thursday to finish the models, The Associated Press reported.

The prototypes must meet guidelines set out by the Customs and Border Protection agency, which include making the wall 18 to 30 feet high and the ability “to withstand at least an hour of punishment from a sledgehammer, pickaxe, torch, chisel or battery-operated tools,” according to the AP.

Six construction companies from Mississippi, Maryland, Alabama, Texas and Arizona are building the prototypes for a combined estimate of $20 million, paid by Customs and Border Protection, according to NPR.

The agency will later evaluate the wall prototypes.

"We want a better barrier. One that is hard to scale, hard to penetrate and hard to tunnel under," said Roy Villareal, chief of the San Diego Border Patrol, to NPR. "We're hoping innovation from private industry combined with our experience generates the next evolution of border security infrastructure.”

Still, the proposed border wall is far from being started, according to Time magazine.

Funding for the wall, which is now estimated to be about $1.6 billion, remains at a standstill in Congress. Most recently, Democrats called for any of the wall’s funding to be removed from any bill that would reform the Deferred Action for Childhood Arrivals program, an Obama-era plan that kept 800,000 undocumented immigrants in the U.S., according to Time.

Trump reportedly made a deal with the Democrats to reform DACA, as long as he received border wall funding, according to Vox.

"The real issue with building a border wall is what the Congress does, not what the contractors do ... The price tag on this is enormous," said Doris Meissner, a senior fellow at the nonpartisan Migration Policy Institute, to NPR.

Leaders of San Diego and California have condemned the wall, too. The Golden State filed a lawsuit with the Trump administration over the plan to build the wall, Reuters reported.