An internal Border Patrol report illustrates that a dramatic shift in where people are arrested trying to cross the U.S.-Mexico border has accelerated this year. More arrests are taking in place in South Texas, rather than further west.

The report obtained by The Associated Press shows that from Oct. 1 through May 17, agents in the southernmost tip of Texas made over 148,000 arrests, on pace to match 2013's total in less than eight months. Just a year after surpassing Tucson, Arizona, as the border's arrest leader for the first time, the Rio Grande Valley is now more than 85,000 arrests ahead of that sector.

Border Patrol agent Chris Cabrera says the agency doesn't have the resources in South Texas to handle the increased traffic, and immigrant smugglers exploit that.