The bodies of 27 people, believed to be migrants from Ethiopia, have been “dumped” by the roadside in Ngwerere area north of Zambia’s capital Lusaka.
They are likely to have suffocated to death while in transit, Police Spokesperson Danny Mwale told the BBC.
One survivor found “gasping for air” has been rushed to a local hospital, he said.
Zambia is a transit point for migrants, mostly from the Horn of Africa, who want to reach South Africa.
Mr Mwale said residents of Ngwerere found the bodies on Sunday at 06:00 local time (04:00 GMT).
He said the police believe the migrants are Ethiopian nationals based on the identity documents found on them.
“Our preliminary investigations indicate that a total number of 28 persons, all males aged between 20 and 38, were dumped in Meanwood Nkhosi along Chiminuka road in Ngwerere area by unknown people,” the police said in a statement.
The bodies have been taken to Zambia University Teaching Hospital mortuary.
In neighbouring Malawi, the authorities discovered 25 bodies of Ethiopian migrants in a mass grave in October.