More than a year after a massive influx of Central American child migrants hit crisis levels at the southern U.S. border, the number of unaccompanied children caught trying to cross into the U.S. is back on a surprising uptick. The U.S. Customs and Border Protection agency said it apprehended 5,000 unaccompanied child migrants in October alone, nearly double the figure from the same period last year.

Illegal border crossings usually decline after the summer months, but numbers have remained high through the fall this year. A total of 4,973 unaccompanied children were caught at the border last month, a slight increase from August, when Border Patrol apprehended 4,632 children.

Authorities also took 6,029 family units into custody at the southern border in October, up from 5,158 in August. Similar to last year, the vast majority of these migrants came from three Central American countries: Honduras, El Salvador and Guatemala.

The Department of Homeland Security, which oversees U.S. Customs and Border Patrol, said it has been “closely monitoring this situation” as migration numbers have increased in recent months, according to the Washington Examiner.

October’s numbers aren’t close to the record numbers seen at the apex of last year’s border crisis. Roughly 20,000 children traveling without parents streamed across the U.S. border in May and June of 2014 in a year that saw more than 60,000 children and an additional 60,000 family units try to enter the country.

This year’s numbers look to be only about half those levels. The Washington Office on Latin America, a think tank, projects the U.S. will have apprehended about 36,000 unaccompanied children by the end of this year.

There are no clear-cut explanations for the recent uptick, but the rampant violence and poverty in Guatemala, Honduras and El Salvador that have fueled much of the exodus have continued unabated. All three have among the world’s top murder rates, with El Salvador recently edging out Honduras for the No. 1 spot as conflicts between street gangs and military forces have escalated sharply this year.

The trend also indicates that the Obama administration’s efforts to stem the tide of illegal immigration, primarily through the detention of migrant families and fast-tracked deportation proceedings, may not have tempered migrants’ desire to cross the border. Both those policies have triggered fierce outcries from immigration advocacy groups, which say detention and quick deportations infringe on due process for many people who face the risk of death back home.