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Federal investigators said Saturday that they have retrieved electronic logging components from a semi-truck that apparently blew a tire and slammed into a Greyhound bus in New Mexico, killing eight people, and both of the truck's front tires will be sent to Washington for analysis.

National Transportation Safety Board investigator in charge Peter Kotowski said the driver of the tractor-trailer that collided with the bus Thursday on Interstate 40 near Thoreau, about 100 miles west-northwest of Albuquerque, has not yet been interviewed but arrangements were being made to speak with him.

The bus driver, identified by state police as Luis Alvarez, was killed in the crash. Greyhound said he had 27 years of experience with the company. There were 48 people on the bus, including the driver.

Five of the eight killed were identified Saturday by the New Mexico Office of the Medical Investigator as Sadie Thomas, 50; Charla Bahe, 34; Terry Mason, 45; Veronica Jean Williams, 49; and Alvarez, 50.

"We know there are other families who are still waiting for word of their loved ones and we are using several identification methods to make those identifications," Dr. Kurt Nolte, chief medical investigator, said in a statement. "My heart goes out to the families of these victims," he said.

The driver of the tractor-trailer also was hurt with what has been described as non-life-threatening injuries.

"Unfortunately, incidents like this are what drives improvements in highway safety so these types of things don’t happen again," Kotowski said Saturday at a news conference in Gallup, New Mexico.

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He expressed condolences to the families involved in the crash and wished the injured a speedy recovery.

The 2017 Freightliner semi-tractor-trailer, owned by JAG Transportation out of Fresno, California, was traveling east on I-40 at around 12:30 p.m. Thursday, when the front driver's-side tire failed and the tread separated from the case, New Mexico State Police said.

The tire failure sent the truck across the median separating the eastbound and westbound lanes and into oncoming traffic, and the tractor-trailer collided head-on with the westbound Greyhound bus, police said.

The entire front end of the bus appeared destroyed. All of those killed were on the bus, state police said, and more than 20 passengers were injured.

A passenger on the bus, Rachel Cunningham, said, "The side of the bus where we get on was opened up like a can of sardines." Another survivor said, "It just felt like an A-bomb go off."

Kotowski said that components of the tractor-trailer's electronic logging device and the engine control module have been recovered but data had not yet been downloaded.

Since December all commercial vehicles were required to be equipped with an electronic logging device connected to the truck, he said, and they can help determine hours of service. A similar device has been recovered from the bus.

Both tires will be examined because they share a common axle and "they are of compatible manufacture dates, so to give us an idea about tire wear" and to compare the two, he said. The other tires on the truck were identified as not having any problems, he said.

Kotowski said investigators have subpoenaed information for blood from both drivers for toxicological purposes, as well as medical records, which he said is part of the NTSB’s normal process.

One of those injured was a pregnant woman who gave birth to twins early because of the impact, said the obstetrician who treated her. The boy and girl were reported to be around 3 pounds each.

"They did very well for babies their size and their age," Dr. Colin Berry said.

The Greyhound bus was equipped with three-point seat belts, and the driver of that vehicle gave a safety briefing to passengers before the St. Louis-to-Los Angeles trip began, Kotowski said.

Investigators will also look at the roadway and the median separating the eastbound and westbound lanes, and whether a depression in the median could have affected the movement of the tractor-trailer as it traveled across it, he said.