The acting deputy secretary of homeland security warned employees Saturday that "there may be a heightened threat" against them, according to a memo obtained by CBS News. The warning comes amid the increasing furor over the Trump administration's "zero tolerance" immigration policy.

"This assessment is based on specific and credible threats that have been levied against certain DHS employees and a sharp increase in the overall number of general threats against DHS employees -- although the veracity of each threat varies," says the message from Claire M. Grady. "In addition, over the last few days, thousands of employees have had their personally identifiable information publically [sic] released on social media."

The memo recommends numerous safety precautions, including not displaying work badges in public, being careful with public conversations and using caution on all social networks. It also recommends DHS employees "always keep doors and windows locked" and "be aware of unexpected changes in and around your home."

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DHS employees are encouraged to call 911 if they feel threatened and if local law enforcement doesn't respond, to call Federal Protective Service.

Grady says she is "eternally grateful" for all the work DHS employees have been putting in, but "there are those who misconstrue your work in a negative way or seek to disrupt your work to advance outside agenda."

The Trump administration enacted a "zero tolerance" policy against undocumented immigrants entering the country in April, detaining parents and placing children in government-contracted shelters. Earlier this week amid intense backlash, President Trump signed an executive order temporarily suspending family separation but said "zero tolerance" is here to stay. The coverage of the controversy has dominated the news for over a week.

On Thursday, WikiLeaks published a database identifying more than 9,000 Immigration and Customs Enforcement (ICE) employees, according to The Washington Post. According to the Post, the database included information such as employees' publicly available personal information and job history scraped from LinkedIn and their LinkedIn profile pictures and information on their educational background and the city and state in which they're based.

As anger over the issue has grown, protesters on Tuesday disrupted Homeland Security Secretary Kirstjen Nielsen's dinner at a Mexican restaurant. On Friday, White House press secretary Sarah Huckabee Sanders was asked to leave a restaurant in Virginia. The owner told The Washington Post she asked Sanders and her party to leave because "this feels like the moment in our democracy when people have to make uncomfortable actions and decisions to uphold their morals."

There were protests held nationwide Saturday over immigration as elected officials demanded access to the shelters where children are being held.

Late Saturday, the Department of Health and Human Services (HHS) said in a statement that 522 children had been reunited with their families. Those children were in the custody of Customs and Border Protection.

HHS said that as of June 20, 2,053 separated minors were in the custody of HHS. HHS said it is "working with relevant agency partners to foster communications and work towards reuniting every minor and every parent or guardian via well-established reunification processes."

Major Garrett contributed reporting.