More Undocumented Kids, Especially Girls, Crossing the Border: Report
U.S. Customs and Border Protection agents work at a processing facility, June 18, 2014, in Brownsville, Texas.

Unaccompanied girls fleeing Central America and caught at the Southwest border has increased 77% since last year, and far more rapidly than the number of boys, according to a new report by the Pew Research Center.

The analysis, which looks at data provided by the Department of Homeland Security via a Freedom of Information Act, shows that while the number of girls under 18 detained at the U.S.-Mexico border has jumped significantly, the number of boys went up only 8 percent in the same period.

While boys have historically made up the majority of those apprehended at the border, the stark rise in girls represents a "change in who is coming across the border," Mark Hugo Lopez, director of Hispanic research at the Pew Research Center told ABC News.

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In fiscal year 2013, teenagers, particularly teenage boys, made up the bulk of those crossing the border," Lopez said. "And while they still do make up the bulk of those crossing the border, we've seen a spike in the number of children and the number of girls and that's different from 2013. … The growth in unaccompanied kids this year has been driven in large part by more children and more girls crossing the border illegally. That is a change from last year."

This data is a follow-up on Pew's report earlier this week showing that pre-teens account for the sharpest spike in unaccompanied child migrants.

When looking at the gender breakdown for those under 12, Pew found a 140% increase in girls apprehended and 100% increase among boys.

But probably most shocking in their analysis is the difference between boy and girl unaccompanied teenagers apprehended.

Teenage girls saw an increase of 62% this year, but teenage boys have seen almost no change - only 2%.

"Teenage boys have been a big point of this unaccompanied minors story, but many of those teenage boys 15,16,17 years of age, to the higher end - these are young people who in many respects may be of working age," Lopez said. "More interesting question is why have we seen the surge or spike in children and teenage girls."

Lopez said that spike is being driven largely by those fleeing violence in Honduras and El Salvador, and according to the Department of Homeland Security, poverty in Guatemala.

Honduras had the highest 2012 murder rate in the world with 90.4 homicides per 100,000 people, and El Salvador had 41.2, according to a report by the United Nations Office on Drugs and Crime.

Honduras is first and El Salvador is second when looking at all unaccompanied girls apprehended this year by country, according to Pew's analysis.

President Obama is meeting today with the leaders of the three countries - Honduras, Guatemala and El Salvador - at the White House to discuss the flow of children.

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