The Trump administration has repeatedly denied that its policy is to separate children from their parents when families cross the US border illegally.

But its own internal documents contradict that.

The Department of Homeland Security's website put out a press release on Friday saying it would separate children from their families.

A "zero tolerance" policy from Attorney General Jeff Sessions mandates that anyone illegally crossing the border be treated like a criminal.

The Trump administration has repeatedly sought to distance itself from its policy separating children from their parents when families cross the US border illegally, but its own internal documents contradict those efforts.

President Donald Trump had previously tried to blame the policy on Democrats, but over the weekend his secretary of homeland security, Kirstjen Nielsen, flat-out denied that such a policy existed.

"We do not have a policy of separating families at the border. Period," Nielsen tweeted.

But the Department of Homeland Security does separate children from their parents at the border, and it just put out a press release about it on Friday, explaining its new "zero tolerance" policy for border crossers.

From the DHS website:

"The Attorney General directed United States Attorneys on the Southwest Border to prosecute all amenable adults who illegally enter the country, including those accompanied by their children, for 8 U.S.C. § 1325(a), illegal entry. "Children whose parents are referred for prosecution will be placed with the Department of Health and Human Services (HHS), Office of Refugee Resettlement (ORR)."

Another FAQ section deals with questions including "Why Are Parents Being Separated From Their Children?"; "Where Are Children Going?"; and "What Happens to Children in HHS Custody?"

An image of the memo from the Department of Homeland Security. DHS.gov

The DHS made a step-by-step guide for detained adults who are trying to reach their children called "Next Steps for Families."

Furthermore, the rise of facilities that house children separated from their families at the border during Trump's administration has been well documented.

Nielsen's real argument is that border crossers are criminals

Mexicans at the US-Mexico border fence on May 1, 2016, in Tijuana, Mexico. Getty Images

Nielsen continued: "For those seeking asylum at ports of entry, we have continued the policy from previous Administrations and will only separate if the child is in danger, there is no custodial relationship between 'family' members, or if the adult has broken a law."

Unauthorized border crossings have always been illegal, but previous administrations did not criminally prosecute all border crossers the way Trump's attorney general, Jeff Sessions, has.

Detainees in the US who are charged with criminal wrongdoing have always been separated from their children; by treating all adult border crossers as criminals, Trump's administration has therefore crafted a policy that leads families to be separated at the border.