The new figures, obtained through a Freedom of Information Act request by the Pew Research Center, provide the first publicly available detailed portrait of the age and home country of child migrants—unaccompanied and accompanied– caught at the U.S.-Mexico border from Oct. 1, 2012, to May 31, 2014. The time period covers the previous fiscal year and two-thirds (8 months) of the current one.

Federal and state officials are scrambling to address the record number of unaccompanied minors (those traveling without a parent or guardian) apprehended at the U.S.-Mexico border in recent months, which has surged by tens of thousands. Media reports have described hundreds of children packed into holding facilities in Texas and across the Southwest, sleeping with thermal blankets and overwhelming the U.S. Border Patrol. President Obama has requested $3.7 billion to respond to what he has called a “humanitarian crisis,” and some Republican lawmakers are readying their own bills.

From October through the end of May, 46,932 unaccompanied children, nearly all from Mexico and Central America, were taken into custody, according to data obtained from U.S. Customs and Border Protection. Recently released figures show that by the end of June, that number had risen to 57,525.