The overcrowded pickup truck that slammed into a tree and killed 14 undocumented immigrants in Texas lost control because its right tire came apart, authorities said.

Investigators said they were unsure if the tire unraveled because it was too old, or because of a manufacturing issue.

Nine passengers remain hospitalized. With little more than photographs and fingerprints, authorities have been trying to identify the ones who were killed in one of the nation's deadliest immigrant smuggling accidents.

Twenty three people, many of them undocumented immigrants from Mexico, Honduras and Guatemala, were crammed onto the bed and cab of the pickup truck when it veered off a rural highway 90 miles southeast of San Antonio.

"More than likely the crash was caused by front right tire separation," Texas Department of Public Safety spokesman Gerald Bryant said Tuesday. The investigation into the crash continues, but it appears layers of the tire had come apart, Bryant said.

Eleven people died at the scene, including at least two children. Three more died later at hospitals.

The victims — men, women and children — were carrying toothbrushes, toothpaste and changes of socks and underwear but no identification.

"It's the worst single-vehicle wreck I've worked in my 40 years in the funeral business," said Adrian Fulton, a local funeral home director who picked up the 11 people who died at the scene. Fulton estimated their ages from 8 to 30, and he said Homeland Security Investigations agents came Monday to photograph and fingerprint the dead.

Federal immigration agents are looking into the human smuggling aspect of the case, while public safety authorities are investigating the cause of the crash in Goliad County, about 150 miles northeast of the Mexican border. The crash scene is less than an hour's drive from the site of the nation's most deadly immigrant smuggling case, where 19 immigrants died in 2003 after being placed in a sweltering trailer.

Six of those who died in Sunday's crash were still inside the cab of the mangled vehicle and one was in the truck's bed when emergency crews arrived at the scene, said Texas Department of Public Safety spokesman Gerald Bryant. Others were scattered on the roadway and in a ditch between the pavement and the fence line where the truck stopped.

Bryant said he saw at least two young children among the dead.

"This is the most people I've seen in any passenger vehicle, and I've been an officer for 38 years," he said.

The Mexican consulate confirmed that one 22-year-old man from Tamaulipas, a state bordering South Texas was among the dead. In a statement, the Guatemalan government said that at least two Guatemalans died in the accident, a 27-year-old man and a 22-year-old woman.

Crashes of vehicles overloaded with undocumented immigrants moving north from the border occur periodically, often as they attempt to evade authorities.

It is not uncommon for human traffickers to try to maximize profits by over-loading vehicles with illegal immigrants as they head north from the Texas-Mexico border.

In April, nine Mexican immigrants died near the border when the teenage driver of their van crashed after fleeing Border Patrol. There were 18 people in that minivan.

In that case, six adults face a variety of federal charges and the 15-year-old driver was charged in state court with nine counts of murder.

Based on reporting by The Associated Press. 

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