Secretary of Housing and Urban Development Ben Carson speaks to employees of the agency in Washington, U.S., March 6, 2017. Thomson Reuters

Newly minted Housing and Urban Development (HUD) Secretary Ben Carson appeared to refer to slaves as "immigrants" in an address to department employees on Monday that often veered off-topic.

"This is what America is about, a land of dreams and opportunity," Carson said, according to a transcript posted on Twitter by NBC's Bradd Jaffy.

"There were immigrants who came here in the bottom of slave ships, worked even longer, even harder, for less," he continued. "But they too had a dream that one day their sons, daughters, grandsons, granddaughters, great-grandsons, great-granddaughters might pursue prosperity and happiness in this land."

Carson's comments likening slaves to immigrants set off a firestorm on Twitter.

And the NAACP responded incredulously:

Carson's comments about slaves came after a lengthy tangent about the intricacies of the human brain.

"Every human being, regardless of their ethnicities, or their background, they have a brain, the human brain," said Carson, a retired neurosurgeon. "There is nothing in this universe that even begins to compare with the human brain...I could take the oldest person here, make a little hole right here on the side of the head, and put some depth electrodes into their hippocampus and stimulate and they would be able to recite back to you, verbatim, a book they read 60 years ago."

Carson, an early primary challenger to Trump, was confirmed by the Senate and sworn in as HUD secretary last week.