WASHINGTON (Reuters) - Efforts by the Obama administration to clamp down on convicted criminals living illegally in the United States resulted in a higher percentage of them being deported in 2015, according to figures released by the Department of Homeland Security (DHS) on Tuesday.

For the fiscal year that ended on Sept. 30, 91 percent of undocumented people removed from the United States by DHS’s Immigration and Customs Enforcement (ICE) had been previously convicted of crimes, up from 86 percent in fiscal 2014 and 67 percent in 2011, the agency said.

“Last year’s removal numbers reflect this department’s increased focus on prioritizing convicted criminals and threats to public safety, border security and national security,” Homeland Security Secretary Jeh Johnson said in a statement.

Some Republican members of Congress have criticized the Obama administration for focusing on convicts, thus easing the threat of deportation for other undocumented immigrants.

In releasing data on U.S. apprehensions and deportations of undocumented residents during the period from Oct. 1, 2014 to Sept. 30, 2015, DHS also touted a significant decrease in those detained at the southwest border with Mexico.

The 337,117 Customs and Border Protection (CBP) apprehensions were the second-lowest number since 1972, DHS said. Last year’s arrivals of undocumented immigrants from El Salvador, Guatemala and Honduras were down sharply from the previous year.

A DHS official who briefed reporters said the drop “indicates investments we made in border security are proving effective and we’re seeing fewer attempts at crossing the border.”

That ignores a recent reversal in which a rapidly growing number of Central Americans are again showing up at the southwestern border with Mexico without immigration papers.

According to CBP data, during the first two months of this fiscal year (October-November), the arrival of children under 18 traveling without an adult relative was up 106 percent over the same period the previous year.

For undocumented families, the number, according to CBP, rose by 173 percent.

DHS officials did not explain the reasons for the big jump.

Overall, DHS said it apprehended 406,595 undocumented people nationwide in the year that ended Sept. 30 and deported 462,463. In the previous year, CBP apprehended 486,651 people and DHS deported 577,295.