Here's what's going on with the children separated at the border

We've seen a flurry of recent activity from politicians and protesters trying to rectify the situation -- yet many undocumented children are still scattered across the country.

Here's what we know and don't know about the complicated situation and what's next:

What we know

-- More than 2,500 undocumented children have been separated from their parents in the two months since President Donald Trump's zero-tolerance policy took effect.

The policy meant any adult caught crossing the border illegally would face federal prosecution. And that led to children getting sent to federal shelters across the country as their parents' criminal cases progressed.

-- The majority of those children have not been reunited with their parents. Government statistics released over the weekend showed more than 2,000 were still in federal custody, and just over 500 had been reunited with their parents.

-- Trump said he wants the US to deport people without judicial proceedings. "We cannot allow all of these people to invade our Country," he tweeted Sunday.

"When somebody comes in, we must immediately, with no Judges or Court Cases, bring them back from where they came," he continued. "Our system is a mockery to good immigration policy and Law and Order. Most children come without parents..."

-- Secretary of Defense James Mattis said two military installations in Texas -- the army's Fort Bliss and Goodfellow Air Force Base -- could be used to temporarily house migrants. Mattis said the military is not involved in the politics of the situation. "For us, it is a logistics support effort," he said Monday.

-- After widespread criticism over the difficulty in finding separated relatives, the government is working to better organize databases linking the parents' and children's information, federal officials said.

What we don't know

-- Even though Trump signed an executive order saying families would not be separated in the future, there's no timeframe on when the roughly 2,000 children who are still separated will see their parents again.

The administration released a plan to reunite those children with their families -- but only after the parents' deportation proceedings are completed. The families will either be reunited before deportation or, if the parent is released from detention, after the parent applies to serve as the child's sponsor under Health and Human Services rules.

-- It's still unclear who will take responsibility for linking parents with children. None of the agencies involved in the process have been designated as the central keeper of both parents' and children's data with the responsibility of putting them back together at the end.

-- We don't know if every child will be successfully reunited with his or her parent. Wendy Young, president of the advocacy and legal support group Kids in Need of Defense, said the process is "incredibly challenging."

"What I fear is that it might, in some cases, be impossible," she said.