Multiple people were killed and dozens more were injured when a semi-trailer and a Greyhound bus carrying 49 passengers crashed on a northwest New Mexico interstate on Thursday afternoon, authorities said.

State Police provided few immediate details about the incident on Interstate 40 near Thoreau, about 100 miles west-northwest of Albuquerque, including the number of dead and injured.

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. University of New Mexico Hospital in Albuquerque said it was expecting six patients, three of whom were in critical condition.

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

NBC affiliate KOB of Albuquerque published a photo showing the semi-trailer on its side and the bus off the road with severe damage to its front left side.

The National Transportation Safety Board said it was sending a team to investigate.