WASHINGTON (Reuters) - U.S. border agents are on pace to arrest about 16 percent fewer people this month at the southwest border than in May, according to preliminary figures provided by an official at the Department of Homeland Security.

FILE PHOTO: A man raises his hands after being found by a border patrol agent in Goat Canyon after he illegally crossed into the U.S. from Mexico near San Diego, California, U.S., June 12, 2018. REUTERS/Adrees Latif

If current trends continue, about 34,000 people will be apprehended attempting to cross the U.S.-Mexico border illegally in June, said the official, who requested anonymity because the numbers are not final.

The drop comes in the wake of President Donald Trump’s “zero tolerance” policy, implemented in May, in which federal agencies coordinate to prosecute all immigrants apprehended entering the United States illegally.

Under the policy, parents are held in federal detention pending prosecution, while their children are sent to shelters or foster homes, often far from their parents and with no clear way to contact them.

The drop in border apprehensions this month could be a response to the policy or a result of normal month-to-month fluctuations. The reduction in numbers is far less dramatic than in the months following Trump’s taking office in January 2017.

In May, border officials arrested 40,344 people at or near the Southwest border, the highest number since Trump took office.

Politico previously reported a drop in arrests based on data from June 1-16. In the week that followed, apprehensions dropped further, the DHS official said.

Trump administration officials have said the zero tolerance policy is needed to secure the border and deter illegal immigration. It has resulted in more than 2,000 children being separated from their parents, and Trump has faced enormous political pressure to reverse course.

On June 20, he partly walked the policy back, issuing an executive order calling for families to be detained together. A federal judge in San Diego ordered the government on Tuesday to rapidly reunite separated families.

Border apprehensions plummeted during the first few months of Trump’s presidency, to a low of 11,126 in April 2017, but have since crept back up to levels comparable with those during the Obama administration.

It is unclear how much of an influence Trump’s recent hardline policies had on the drop in arrests in June. Randy Capps, director of research for U.S. programs at the Migration Policy Institute, a non-partisan group, noted that 34,000 arrests at the southern border this month would be almost the exact same number of arrests as in June 2016, and twice as high as June 2017.

“There is no evidence yet that zero tolerance has substantially affected either the level of apprehensions this month or the seasonal pattern of slight declines from May to June,” Capps wrote in an e-mail.

DHS officials did not respond to a request for comment. A CBP spokeswoman said official June numbers will be released on July 9.