Forty-two immigrants from Malawi were found dead in a truck in central Tanzania, having perished from asphyxiation, the deputy interior minister said.
"They died of suffocation and had no food," Pereira Silima said on Tuesday.
"There were more than 100 people in the truck," a local administration official told AFP news agency, speaking on condition of anonymity.
"After he had learnt of the dead bodies, the driver abandoned the truck and ran away."
The bodies were discovered in the truck in Dodoma province, about 400km (250 miles) west of Dar es Salaam.
In December, 20 Somali immigrants were found dead in Tanzania.
Foreign ministry spokesman Isaac Nantanga said at the time that an increasing number of Ethiopians and Somalis were crossing the country to make their way to South Africa, the continent's top economy.