Some 545 children have yet to find their migrant parents after being separated by U.S. President Donald Trump's 'Zero Tolerance' Policy.

A filing from the American Civil Liberties Union (ACLU) on Tuesday revealed that federal-appointed lawyers tasked to identify migrant families separated by the Trump administration stated that there are still 545 children whose parents they were unable to track down.

According to the filing, the 545 children account for about two-thirds of those left in the U.S. after their parents were deported to Central America.

A report by NBC News stated that in 2018, the Trump administration imposed a "zero-tolerance policy," which caused the separation of migrant parents from their children at the southern border of the U.S.

Later on, it was revealed by the administration that they have already started to separate families who live in some parts of the border as part of a pilot program in 2017.

In connection with these incidents, the ACLU, along with other pro-bono lawyers, were given the task to find the families that have been separated by the pilot program.

Under the pilot program, more than 1,000 parents have already been separated from their children and were deported before a federal judge gave out the order to find them.

The situation is very different from what happened to the 2,800 families separated under the "zero tolerance" policy. Most of the families in 2018 remained in police custody until an executive order was imposed, ending the policy, Yahoo! News reported.

In a statement by ACLU Immigrants' Rights Project deputy director Lee Gelernt, it is critical to find who was responsible for what he dubbed as a "horrific" practice. He also noted that this needs to be done without forgetting the need to reconnect the families who remain separated until the present.

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Gelernt also added that he is still unable to give an answer as to when all the families can be found. But he also assured that they would not give up looking until the last of the 545 children is reunited with his/her parents, no matter the length of time.

Moreover, he noted that it was very tragic how many parents were deported to Central America while their children remained in foster homes or were left with distant relatives.

"There is so much more work to be done to find these families," Gelernt added.

In addition, Gelernt said that there were also some families who chose to keep their children in the U.S. under the care of family members or sponsors. 

He added that this is due to their fear of what may happen to their children if they return to their home country.

On top of this, a group known as Justice in Motion is also searching for separated parents in Central America and Mexico. 

According to the group, they have already located many parents who have been deported and are still trying to reach hundreds of others, The Hill reported.

However, the group noted that they are also facing several challenges, especially with the COVID-19 pandemic.

Back in 2018, a court order directed the administration to reunite families that were separated under the zero-tolerance policy.

Meanwhile, the Department of Homeland Security has yet to respond to requests for comments regarding the 545 children estranged from their parents.

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