At least 64 people, believed to be Ethiopians, are thought to have suffocated to death in a lorry that had crossed into Mozambique from Malawi, officials say.
Fourteen survivors were discovered in the vehicle in the western province of Tete early on Tuesday morning.
The immigration service had stopped the container truck in the town of Moatize, according to Tete provincial director of health, Carla Mosse
She said investigations were ongoing to discover how the occupants died - but said asphyxiation was the likely cause of death.
Amélia Direito, spokesperson for the National Migration Service in Tete, said the driver had not wanted to stop the vehicle when asked.
She explained that her colleagues had heard noises from the lorry and suspected that migrants might be inside.
It is a well-known trafficking route for people hoping to get further south to South Africa.
The 14 survivors will be screened for Covid-19, Ms Direito said.