46 migrants found dead in abandoned trailer in San Antonio, Texas

Forty-six people were found dead in a sweltering tractor-trailer that was abandoned on a remote back road in San Antonio in what marked the latest tragedy to claim the lives of migrants smuggled across the border from Mexico to the U.S. Sixteen people were hospitalized, including four children.

Those identified so far hailed from North and Central America; incident comes amid immigration law battles

Law enforcement officers work at the scene where dozens of people were found dead inside a tractor-trailer Monday in San Antonio, Texas. (Eric Gay/The Associated Press)

Forty-six people were found dead in a sweltering tractor-trailer that was abandoned on a remote back road in San Antonio in what marked the latest tragedy to claim the lives of migrants smuggled across the border from Mexico to the U.S. Sixteen people were hospitalized, including four children.

A city worker in southwest San Antonio heard a cry for help from the truck shortly before 6 p.m. Monday and discovered the gruesome scene, police Chief William McManus said. Hours later, body bags lay spread on the ground near the trailer as a grim symbol of the calamity.

"I am heartbroken by the tragic loss of life today and am praying for those still fighting for their lives," said Alejandro Mayorkas, the secretary of the Department of Homeland Security, responsible for enforcing U.S. immigration laws. "Far too many lives have been lost as individuals — including families, women, and children — take this dangerous journey."

Roberto Velasco Alvarez, head of the North America department in Mexico's Foreign Relations Department, said on Twitter that it is known that 22 of the deceased are from Mexico, seven are from Guatemala and two are from Honduras.

"Our condolences," he tweeted. "All responsible will be brought to justice."

South Texas has long been the busiest area for illegal border crossings. Migrants ride in vehicles though Border Patrol checkpoints to San Antonio, the closest major city, from which point they disperse across the United States.

San Antonio Police Chief William McManus, centre, briefs media and others at the scene where the bodies were discovered. (Eric Gay/The Associated Press)

No water found in trailer

Of the 16 taken to hospitals with heat-related illnesses, 12 were adults and four were children, said fire Chief Charles Hood. The patients were hot to the touch and dehydrated, and no water was found in the trailer, he said.

"They were suffering from heat stroke and exhaustion," Hood said. "It was a refrigerated tractor-trailer, but there was no visible working AC unit on that rig."

Those in the trailer were part of a presumed migrant smuggling attempt into the United States, and the investigation was being led by U.S. Homeland Security Investigations, McManus said.

Three people were taken into custody, but it was unclear if they were definitively connected with human trafficking, McManus said.

It's among the deadliest tragedies that have claimed thousands of lives of people attempting to cross the U.S. border from Mexico in recent decades. Ten migrants died in 2017 after being trapped inside a truck that was parked at a Walmart in San Antonio. In 2003, 19 migrants were found in a sweltering truck southeast of San Antonio.

Big rigs emerged as a popular smuggling method in the early 1990s amid a surge in U.S. border enforcement in San Diego and El Paso, Texas, which were then the busiest corridors for illegal crossings.

As crossing became exponentially more difficult after the 2001 terror attacks in the U.S., migrants were led through more perilous terrain and paid thousands of dollars more.

Heat poses a serious danger, particularly when temperatures can rise severely inside vehicles. Weather in the San Antonio area was mostly cloudy Monday, but temperatures approached 100 F.

Pandemic measure still in effect

U.S. Customs and Border Protection reported 557 deaths on the southwest border in the 12-month period ending Sept. 30, more than double the 247 deaths reported in the previous year and the highest since it began keeping track in 1998. Most are related to heat exposure.

Migrants have been expelled more than two million times under a previously rarely used health order that the Donald Trump administration invoked in March 2020 as the coronavirus pandemic began to rage. The Title 42 authority denies migrants a chance to seek asylum but encourages repeat attempts because there are no legal consequences for getting caught.

Reaction from Democratic congressman who represents San Antonio:

Joe Biden's administration made plans to end Title 42 effective late May but a federal judge, in response to legal action launched by 24 states, blocked the plan. The Biden administration decision was made without sufficient consideration on the effects the move could have on public health and law enforcement, the Louisiana-based judge ruled.

Title 42 authority has been applied unevenly across nationalities. Mexico has agreed to take back migrants from Guatemala, Honduras, El Salvador and Mexico — and limited numbers from Cuba and Nicaragua. High costs, strained diplomatic relations and other considerations have made it more difficult to remove migrants from other countries, who must be flown home.

Reaction from Republican senator from Tennessee:

Aaron Reichlin-Melnick, policy director at the American Immigration Council, wrote that he had been dreading such a tragedy for months.

"With the border shut as tightly as it is today for migrants from Mexico, Guatemala, Honduras and El Salvador, people have been pushed into more and more dangerous routes. Truck smuggling is a way up," he wrote on Twitter.

Title 42 is one of two major surviving Trump-era policies to deter asylum at the border, along with the Migrant Protection Protocols (MPP), better known as "Remain in Mexico." The U.S. Supreme Court heard arguments in the spring on the program the Biden administration is trying to end, and is expected to render an opinion on the case as soon as Wednesday.

MPP forces asylum-seekers to wait in Mexico for hearings in U.S. immigration court. Activists argued that Mexico does not constitute a safe third country under immigration law, while opponents have argued that it outsources enforcement and therefore gives great leverage over U.S. policy to a foreign country.

With files from CBC News