The grim discovery comes just days after police found the dismembered, decapitated bodies of 18 people in two abandoned vehicles in western Mexico.
The killings appear to be the latest in a string of brutal murders linked to a continuing conflict between rival drug gangs.
Forty-nine mutilated bodies have been found dumped by a roadside near the city of Monterrey in northern Mexico.
Security officials said the 43 men and six women had been decapitated and had their hands cut off, making identification difficult.
They blamed the killings on a conflict between rival drugs gangs – a note left with the bodies said they had been killed by the Zetas cartel.
It is the latest in a series of recent massacres in northern Mexico.
The Zetas have been fighting the Gulf and Sinaloa cartels for control of smuggling routes into the US.
The bodies were found at 04:00 local time (09:00 GMT) in Cadereyta municipality on the road from Monterrey to Reynosa on the US border.
Security officials said the bodies appeared to have been killed at another location up to two days ago and dumped from a truck.
“We know from the characteristics that this is the result of violence between criminal gangs, it is not an attack on the civilian population,” Nuevo Leon State security spokesman Jorge Domene said.