While there were some concerns that the victims were a contingent of migrant workers, Hidalgo said the bus simply picked up anyone who stopped it on its route to the northern city of Monterrey.
The bus collided with a tanker truck loaded with fuel in the northern border state of Tamaulipas.
Prosecutors said in a statement that “the crash may have occurred because one of the fuel tanks became detached.”
Both vehicles burned out completely in the collision. Police photos showed the bus had become a tangle of smoking, charred metal.
The driver of the tanker apparently survived and is being examined. The bus had apparently departed from the central state of Hidalgo and was en route to Monterrey.
The articulated lorry pulled two tank trailers in a row. Such double container trucks have been involved in numerous fatal accidents in the past.
Because weight restrictions and security controls are lax in Mexico, there have been calls in the past to ban the extremely heavy and unwieldy trucks.