At least eight people were killed and dozens more were injured when a semi-trailer and a Greyhound bus carrying 49 people crashed on a New Mexico interstate, authorities said Friday morning.

New Mexico State Police said the semi-trailer blew out a tire, crossed the median into oncoming traffic and collided with the bus on Interstate 40 near Thoreau, about 100 miles west-northwest of Albuquerque. The agency said seven people were confirmed dead at the scene; the driver of the truck suffered non-life-threatening injuries, it said.

"Our sympathies are with the families whose loved ones were involved in this crash," the New Mexico Office of the Medical Investigator said. "Our commitment to investigate deaths to serve the living will drive our efforts to bring some closure and peace to these families, as well as to support public safety efforts."

The initial death toll after the accident was seven, but the University of New Mexico Hospital in Albuquerque said Friday that one of the 11 patients brought there had died during the night. They noted that they still had nine patients, adding that three adults and one child remained in critical condition.

Gallup Indian Medical Center told NBC News that it was treating about 37 patients, four to six of whom were transported to a trauma center.

Greyhound had initially said 47 passengers were aboard the bus, which was traveling from Albuquerque to Phoenix. No cause had yet been determined, the company said.

The National Transportation Safety Board sent a team on Friday to investigate.

The New Mexico State Police announced Friday morning that both lanes of Interstate 40 had reopened despite a large pile of debris remaining on the shoulder of the roadway.