The exact number of injuries is still under investigation.
How many people were on board?
Passing motorists described a chaotic scene with passengers on the ground and people screaming. In July, three people were killed when a passenger bus rolled into oncoming traffic.
Part of the side of the bus was torn off, in "an awe-inspiring, awful scene".
He saw the rest of the wreckage and stopped to help before coming across the driver of the semi sitting on the shoulder of the highway. Investigators were unsure what cargo the truck was carrying, but Wilson said "there are a lot of vegetables" at the crash site. He did not have any information on the people who were killed, including their ages, genders or where they were from.
The bus began its route in St. Louis Wednesday morning as was scheduled to arrive in Los Angeles Friday morning.
The crash occurred along Interstate 40 in McKinley County, near Thoreau, police said.
Aerial footage by CNN affiliate KRQE showed the bus damaged on the front edge, but upright, in the grass median.
Greyhound says the bus was heading from Albuquerque to Phoenix and there were 47 passengers on board.
"Our first priority is taking care of our passengers and the families, as this has impacted everyone involved", Crystal Booker said in a statement. It forced the closure of westbound lanes of the interstate and traffic was backing up as travelers were diverted.
"We do expect that number to rise", New Mexico State Police spokesman Officer Ray Wilson said on Thursday. Debris from the semi also littered the area. The cause of the accident was not immediately known.
New Mexico State Police are reporting serious injuries among the passengers aboard a commercial bus that crashed along Interstate 40. She deferred comment regarding the crash to the state police.