President Donald Trump has falsely claimed that “tremendous amounts” of the southern border wall he promised during his presidential campaign “have already been built.”

Great briefing this afternoon on the start of our Southern Border WALL! pic.twitter.com/pmCNoxxlkH — Donald J. Trump (@realDonaldTrump) March 28, 2018

The DHS backing of Trump’s falsehood raises questions about the reliability of information from a federal agency that may be key if Trump follows through on his threat to declare a national emergency so he actually can start building his promised wall without congressional approval.

Trump often says construction of his wall already has begun. In 2017, the president won $1.6 million for improved border protection projects. But that was primarily for shoring up or overhauling existing fencing, not for the border wall Trump promises. The spending measure specifically states that none of the money can be used to build any of Trump’s prototype walls.

Nevertheless, DHS over the summer announced on Twitter: “Today marks Potus’ 500th day in office, and just as he promised, the border wall has begun construction.” The press release the DHS tweet linked to touted the “border-wall construction project.”

The project DHS touted had been planned since 2009 and does not involve Trump’s wall. It aims to upgrade 14 miles of a 10-foot high metal barrier with an 18- to 30-foot bollard-style fence.

There are some 650 miles of barriers on the U.S.-Mexico border, and have been since before Trump took office.

Today marks @POTUS' 500th Day in office, and just as he promised, the border wall has begun construction. https://t.co/plaZMq7sIs — Homeland Security (@DHSgov) June 4, 2018

A December DHS statement headlined “Walls Work” further declared: “Under this President, we are building a new wall for the first time in a decade that is 30-feet high to prevent illegal entry and drug smuggling.” DHS was widely criticized for the misleading statement, but didn’t attempt to clarify it.

DHS also has been slammed for peddling suspect statistics. The Trump administration has said that nearly 4,000 people on the FBI terror watchlist have been stopped attempting to enter the country. But DHS Secretary Kirstjen Nielsen failed to point out the number included everyone around the world, with most stopped at airports.

During a presentation on apprehensions at the border by Nielsen in the White House last week, House Majority Leader Nancy Pelosi (D-Calif.) said flatly: “I reject your facts,” The Wall Street Journal reported.

Nielsen responded: “These aren’t my facts. These are the facts.”

Sen. Dick Durbin (D-Ill) called Nielsen’s figures “preposterous.”