Border Patrol agents working the Rio Grande Valley Sector say they have taken more than 800 migrants into custody within a 24-hour period this week, including what they describe as the "single largest group apprehended thus far, this year." 

On Tuesday, agents near La Grulla, Texas first encountered 336 migrants, eight of which were unaccompanied children, according to the Border Patrol.  

"Many within the group suffered from dehydration and exhaustion," the agency said in a statement, adding that the majority of the migrants were from Guatemala. "Border Patrol Emergency Medical Technicians responded and provided medical assistance to those in need before being sent to the hospital for further treatment." 

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Then later that night, McAllen Border Patrol Station agents found 509 migrants traveling in a group near Hidalgo, Texas, comprising of "331 family members, 115 unaccompanied children, and 63 single adults." 

"These apprehensions account for the single largest group apprehended thus far, this year," the Border Patrol said, noting that the migrants hailed from El Salvador, Guatemala, Honduras, Nicaragua, Ecuador and Venezuela. 

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The Rio Grande Valley Border Patrol Sector also says it has made more than 700 rescues of migrants so far this fiscal year. 

"From the river to ranchlands, our agents are doing everything they can to locate and rescue individuals who are lost or distressed, and we are witnessing firsthand that migrants are experiencing the worst as their trek to the border is unforgiving," Chief Patrol Agent Brian Hastings said in a statement.