We're hearing the first accounts from survivors of human smuggling tragedy in San Antonio Texas. They describe their journey from Mexico to the back of a sweltering tractor trailer.

When Adan Lara Vega and six people climbed into the back of that trailer in Laredo, Texas, he says it was pitch black and already full.

An hour into the trip, Vega says people started "crying and asking for water." And as the trailer got hotter, he says people fell into despair.

Investigators estimate more than 100 people were packed inside the truck where temperatures reached more than 100 degrees and people shared a single breathing hole in the wall. The death toll has risen to 10 and many other survivors remain hospitalized. 

In court papers, another survivor says he traveled with a group of nearly 30 people, taking a raft across the Rio Grande and paying more than $700 for protection by the Mexican Zetas drug cartel.

CBS News correspondent Mark Strassmann spoke with a special agent in charge who would not go into detail about the investigation, but he did say the condition that these people were transported in is not uncommon.

Shane Folden is the special agent in charge for homeland security investigations in San Antonio.   

"These organizations consider these people simply a commodity, they don't think of them as people, they look at them from a profit perspective," Folden said.

On Monday, the driver of the semi-trailer, 60-year-old James Matthew Bradley, made his first appearance in federal court.

He faces charges of illegally transporting immigrants for financial gain, resulting in death.