SAN DIEGO (AP) – Immigration authorities caught barely half of the people who illegally entered the U.S. from Mexico last year.

That’s according to an internal Homeland Security report that offers one of the most detailed assessments of border security ever compiled.

The report found that 54 percent of people who entered illegally between border crossings got caught in the 2015 fiscal year. That’s much lower than the 81 percent success rate that Homeland Security cited publicly using a different counting method.

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The report was completed in May, and Homeland Security officials have declined to release it, despite urging from some members of Congress.

The Associated Press obtained a copy from a government official involved in border issues. The official acted on condition of anonymity because the report has not been made public.

(Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)

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