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Story highlights

The drop in March was a sharp departure from annual trends

The numbers marked a 35% drop from February

Washington CNN —  

Apprehensions at the southern border continue to fall dramatically, according to new numbers from Customs and Border Protection – a drop that experts attribute to President Donald Trump’s aggressive immigration enforcement policies.

There were roughly 12,000 total apprehensions at the southwest border in March, according to numbers obtained by CNN that are expected to be released this week. That represents a 35% drop from February and a 63% drop from March 2016.

In 17 years of CBP data, apprehensions had never dropped from February to March, typically rising slightly.

Former Acting Customs and Border Patrol Commissioner David Aguilar said Tuesday at a hearing in front of the Senate’s Homeland Security Committee that through the end of March, immigration officials have seen a 67% drop in illegal crossings from Mexico as compared to the same period last year.

Aguilar attributed the drop to Trump’s hardline position on immigration – a focal point of his campaign and the first few weeks of his presidency.

“This has happened before when – as it relates especially to immigration – when the US stands strong and takes certain actions,” Aguilar said. “This administration said we’re going to address illegal immigration. ICE has started working in the interior unlike other times. So that message resonates.”

CNN was told by current CBP officials on Tuesday that southwest border migration numbers are still being finalized and will be posted at a later date.

Attempts to enter the US illegally can vary based on a variety of factors, often referred to as push and pull. Violent, dangerous or desperate conditions in Central America, where a majority of migrants originate, can push individuals to make the journey north through Mexico. Homeland Security Secretary Kelly has talked about the importance of working with Central American countries to cut back on violence as another element in combating illegal immigration.

Trump’s strict position on immigration is seen as affecting the so-called “pull factors” that attract would-be immigrants. The idea is that word of mouth and media coverage of Trump’s low-tolerance policy for undocumented immigrants can be a deterrent to individuals considering making the journey.