Washington (CNN) Immigration and Customs Enforcement has begun using DNA testing at seven locations along the southern border to identify individuals who pose as families, the agency said Monday.

The implementation of DNA testing along parts of the US-Mexico border is part of a concerted effort by the Trump administration to crack down on illegal immigration, as the number of apprehensions at the border continue to outpace recent years. The DNA testing, in particular, takes direct aim at individuals posing as families amid the increase in families at the border. The administration has argued that people are using children to get into the US, knowing they'll be released.

Out of the 102 family DNA tests administered last week, 85 were found to have a familial connection, ICE said. Seventeen came out negative, and 16 of those were referred for prosecution.

Migrants have to consent to the test, which can provide results in about 90 minutes. The information collected in the DNA test is not stored or shared, ICE says.

The Department of Homeland Security has repeatedly warned that children are being exploited by traffickers to skirt the nation's immigration laws. Currently, the government can't hold migrant children in detention for more than 20 days, often leading to the release of families -- or groups posing as families -- until their immigration court hearing, a practice President Donald Trump has derided as "catch and release."

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