A total of 13 migrants have now been confirmed dead after a massive group last week tried to cross the Rio Grande River near the Texas border. 

Border Patrol agents in the Del Rio Sector, including Border Patrol's Search, Trauma and Rescue (BORSTAR) and riverine agents, responded on Thursday to a large group of people near Eagle Pass, Texas, and apprehended 53 migrants. Customs and Border Protection's (CBP) Air and Marine officials also aided in the mission. 

Thirty-seven of the migrants were rescued as they tried to cross the Rio Grande into the United States. Officials on Friday initially said that agents had discovered eight dead migrants. On Saturday, CBP said the death toll had risen to nine. 

Then CBP Commissioner Chris Magnus tweeted that he was "reflecting on the 13 lives lost ... while they attempted to cross the Rio Grande River at Eagle Pass." 

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Texas border crossing migrants

Migrants are seen crossing the Rio Grande River near Eagle Pass, Texas, on Sept. 3, two days after the massive crossing that led to deaths. (Fox News)

"I appreciate the dangerous work of our Border Patrol to save lives and recover the bodies of the deceased," he added. "Their job is not an easy one and many people don’t realize the toll it can take on those who serve as Agents." 

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Migrants Texas border crossing

Migrants stream across the Texas border on July 13. Eight migrants were found dead Thursday and another 53 were taken into custody as they tried crossing the Rio Grande into Texas, authorities said.  (Fox News)

Across the river, Mexican authorities took into custody another 39 people in relation to Thursday’s attempted crossing.  

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The incident comes as migrants continue to approach the border in a dangerous fashion. 

In June, 53 migrants were found dead inside a tractor-trailer in San Antonio, highlighting the dangerous conditions many face as they try to cross the border illegally. 

Fox News’ Bill Melugin, Adam Shaw and Louis Casiano contributed to this report.