(Bloomberg) -- The discovery of dozens of people dead in a tractor-trailer in Texas is renewing focus on the political standoff over the US-Mexico border, with President Joe Biden’s administration under pressure to crack down both on conventional crossings and extreme alternatives.

At least 50 people died in San Antonio, while others were taken to the hospital, including some under the age of 18. Authorities have launched a human smuggling investigation, and Mexico said that nearly half the dead were its citizens.

The sobering discovery on Monday has put fresh light on the border, where lengthy backlogs, byzantine immigration rules and wrangling over pandemic-era restrictions complicate the options for people to cross legally, leaving some to try and enter illegally through smuggling networks. 

The number of fatalities is strikingly high, and it comes as Biden struggles to reshape the US approach, prompting a fresh wave of criticism from Republicans and border state officials. 

“The loss of life is tragic, it’s unnecessary, and it’s a product of inaction within the federal government over decades,” San Antonio Mayor Ron Nirenberg told CNN on Tuesday. “The people that are responsible for subjecting other people in these conditions should be prosecuted to the fullest extent of the law.”

Biden, in a statement, described the loss of life as “horrifying and heartbreaking.”

“Our prayers are with those who lost their lives, their loved ones, as well as those still fighting for their lives.” Biden said.

“While we are still learning all the facts about what happened and the Department of Homeland Security has the lead for the investigation, initial reports are that this tragedy was caused by smugglers or human traffickers who have no regard for the lives they endanger and exploit to make a profit,” the president said in the statement.

Biden highlighted his announcement in Los Angeles earlier this month of the launch of an anti-smuggling campaign with the country’s regional partners. “In the first three months, we have made over 2,400 arrests, and that work will only intensify in the months ahead,” he said.

“Exploiting vulnerable individuals for profit is shameful, as is political grandstanding around tragedy, and my Administration will continue to do everything possible to stop human smugglers and traffickers from taking advantage of people who are seeking to enter the United States between ports of entry.”

The migrants were found on the southwest edge of Texas’s second-largest city, in an area crowded with auto parts stores, warehouses, mechanic shops and concrete plants. The area has seen issues with human smuggling before, but this is probably the worst, Nirenberg said.

The border has long been an intractable problem for Biden and a potent political cudgel for Republicans. His administration is moving to lift Title 42, a pandemic-era measure that expedited removal of people. Republicans have opposed lifting of the measure, and the effort remains mired in a legal fight.

Congress has done nothing to move on immigration reform or to even confirm nominees to top posts. Biden’s pick to lead US Immigration and Customs Enforcement, Ed Gonzalez, dropped out this week, citing “paralyzing political gridlock that threatens far more than our nation’s border.” Several Republicans opposed Gonzelez’s confirmation, which was stymied for more than a year.

Border States

Republicans have pushed for hard-line measures that echo efforts from former President Donald Trump to build a border wall and physically stop migrants from crossing into the US. 

Texas Governor Greg Abbott, who has advocated for those approaches, was quick to pin blame: “These deaths are on Biden,” he tweeted Monday night, shortly after the news broke. On Tuesday, he touted an effort by the Texas National Guard, previously announced, to use river boats along the Rio Grande to deter people from crossing into the US.

Smuggling cases are often spurred when people have no other option and could be fueled by greater enforcement or more conventional border crossings.

Beto O’Rourke, the Democratic candidate for Texas governor, said the tragedy illustrates the need to strike hard at human smugglers and broaden opportunities for migrants to enter the US. The border situation has been a flashpoint in O’Rourke’s campaign to unseat Abbott.

“This is devastating,” O’Rourke said in an email. “We need urgent action — dismantle human smuggling rings and replace them with expanded avenues for legal migration that reflect our values and meet our country’s needs.”

Democratic and Republican US House members visited south Texas on June 17 to tour the impoverished migrant communities known as colonias. 

“Every state is becoming a border state because drugs are being trafficked across, there’s human trafficking, and the toll is really significant,” Representative Bryan Steil of Wisconsin told reporters after he and three other Republicans took a boat tour of the Rio Grande near McAllen, Texas. “The answer is very simple, there’s a policy solution to this. We need to secure the United States-Mexico border.” 

The White House rejected Republican criticisms, saying the border “is closed” already. 

“We will continue to take action to disrupt human smuggling networks,” Press Secretary Karine Jean-Pierre told reporters Tuesday on Air Force One. “The fact of the matter is the border is closed, which is in part why you see people trying to make this dangerous journey using smuggling networks.”

Mexico’s foreign minister said nearly two dozen of the dead were Mexican citizens, while others were from Honduras and Guatemala. Mexican President Andres Manuel Lopez Obrador said he would discuss immigration during a White House meeting with Biden, previously scheduled for July 12.

Read More: Biden Bid to End Border Expulsions Stopped by Federal Judge

The investigation is ongoing, with Homeland Security Secretary Alejandro Mayorkas also signaling that it’s a suspected case of human smuggling. An Immigration and Customs Enforcement spokesperson said authorities have detained three individuals believed to be part of the smuggling conspiracy.  

Temperatures soared to 103 degrees Fahrenheit (39 Celsius) in San Antonio on Monday, according to Accuweather.com.

The precise number of dead and injured remained unclear. An adolescent male rescued from the truck was in critical condition Tuesday morning at University Health in San Antonio, a spokeswoman said. The second victim taken to that hospital, a 23-year-old woman, was in serious condition. No details on their nationalities were available.

(Updates with details, additional reaction starting in sixth paragraph)

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