Pregnant survivor of New Mexico bus crash gave birth to twins hours later The Thursday crash took place when a tractor trailer collided with the bus.

A pregnant survivor of the New Mexico bus crash that claimed eight lives gave birth to twins hours after the devastating accident, officials said.

The crash took place Thursday when a tire on a tractor trailer blew, causing it to veer into oncoming traffic. The tractor trailer hit a Greyhound bus head-on, according to New Mexico State Police.

The truck, which was carrying produce, was driving on the right lane on eastbound Interstate 40 when the left front tire failed, the tread separating from the tire's case, New Mexico State Police Chief Pete Kassetas said in a press conference Friday afternoon.

The bus then jack-knifed across 50-foot median and entered the westbound lanes, colliding into the front of the bus, Kassetas said.

The police chief said "seconds really matter" in the crash because a few seconds later and the tractor trailer would have crashed into the middle of the bus, which "would have been much more catastrophic."

The driver, identified as 49-year-old Luis Alvarez, was among the dead, Kassetas said. Alvarez was licensed to drive in New Mexico, Kassetas said.

Forty-nine passengers were on board the bus and most were taken to local hospitals with injuries. Seven people died on the scene and one person later died at the hospital, Kassetas said.

The bus originated in St. Louis, Missouri and stopped in Albuquerque to board additional passengers, Kassetas said.

Five children ages 3 to 15 were on the bus and were "all OK," Kassetas said. The bus was equipped with seat belts, a Greyhound spokesperson told ABC news.

The area where the crash occurred is in a "very rural area" with little cell phone service, Kassetas said.

Although multiple agencies responded to the crash, at one point first responders ran out of ambulances to transport victims to area hospitals, the police chief said.

Among those injured was a pregnant woman who delivered twins after the accident.

The mother was listed in stable condition Friday at Rehoboth McKinley Christian Health Care Services while the twins were admitted to the neonatal intensive care unit at the University of New Mexico Hospital, officials said.

Seventeen people -- including the newborn twins -- were still receiving medical attention across five hospitals as of Friday afternoon.

Kassetas commended motorists who stopped at the scene to help get passengers off the bus and administer aid, which he said said several lives.

"It’s amazing. I commend them," he said. "To get ladders out -- to actually enter the bus and get people out -- it’s very difficult to off-board 48 people in a crash like that."

Christopher Jones told ABC News he got to the accident site on Interstate 40 just after the crash.

"There was multiple fatalities that I could see," Jones said, adding that he was "just trying to help other people that were critical and help them calm down."

Jones, who said he used to be a volunteer firefighter and EMT, described the scene as "one of the hardest" he's ever experienced: "It was a pretty rough site."

Investigators are trying to gain access to the electronic driver's logs, which may have been destroyed in the crash. The truck driver was identified as a 35-year-old California resident but was not named.