SAN FRANCISCO/WASHINGTON (Reuters) - U.S. immigration authorities arrested 170 people between early July and late November who came forward to claim migrant children in government custody, according to official data released on Monday, a crackdown advocates say is discouraging relatives from volunteering to take in some of the 14,000 detained children.

Of those arrested, 61 were classified as criminal while the other 109 had only committed immigration violations, said U.S. Immigration and Customs Enforcement spokesman Matthew Bourke.

President Donald Trump won the White House on a promise to crack down on illegal immigrants and he has ordered more aggressive enforcement to dissuade migrants from crossing the U.S. southern border.

U.S. laws and legal precedent limit the time migrant juveniles can be detained, so those caught crossing the border alone are often released to their parents or other close relatives.

About 80 percent of potential sponsors that ICE conducted checks on in that five-month period were in the United States unlawfully, said Bourke.

The Department of Health and Human Services (HHS) cares for the migrant children, while the Department of Homeland Security (DHS) enforces immigration law and oversees ICE.

HHS officials did not immediately respond to a request for comment.

In April, HHS and DHS agreed they would share more information about children and their potential sponsors. That information was not previously routinely shared. HHS now provides immigration authorities with names, dates of birth, and fingerprints of potential sponsors. All adult members of the potential sponsor’s household must also be fingerprinted, something not required in the past.

The government says it wants to ensure that potential sponsors are suitable and properly vetted. But immigrant advocates have criticized the policy change, saying it is scaring parents and other relatives from claiming their children.

On Nov. 28, 112 organizations wrote a letter to DHS Secretary Kirstjen Nielsen and HHS Secretary Alex Azar urging them to reverse the policy.

“Your agencies have taken a process designed to protect children and made it into a tool that uses them to find and deport their families,” they wrote.

In September, senior ICE official Matthew Albence testified to Congress that ICE had arrested 41 people who came forward to sponsor immigrant children. The figures provided by ICE on Monday include the 41 people mentioned by Albence, Bourke said.