TENOSIQUE, Mexico — The United States has detained more children trying to cross the nation’s southwest border on their own over the last year than during any other period on record, surpassing the surge of unaccompanied minors that set off a crisis during the Obama administration, according to new figures released Tuesday.

American immigration authorities apprehended 76,020 minors, most of them from Central America, traveling without their parents in the fiscal year that ended in September — 52 percent more than during the last fiscal year, according to United States Customs and Border Protection.

Mexico is experiencing the same surge. Under pressure from the Trump administration, President Andrés Manuel López Obrador stepped up immigration enforcement and detained about 40,500 underage migrants traveling north without their parents in the same period — pushing the total number of these children taken into custody in the region to more than 115,000.

In interviews, nearly two dozen children who were heading toward the United States said they knew the trip was dangerous — and that if they were caught they could end up in overcrowded, dirty facilities on both sides of the border, without adequate food, water or health care. But they took their chances anyway, looking to escape dead-end poverty, violence and a lack of opportunities to study or work, despite President Trump’s aggressive efforts to block immigration through the southwest border.