A truck, an auto-rickshaw and two mini-trucks used in transporting the stolen item were also seized from the spot on Friday night.
The consignment was being transported from Nalco alumina refinery at Damanjodi in Koraput district to Vishakhapatnam port by train when the theft occurred.
"Around midnight, the miscreants broke open the lock of a bogie of the train which had halted at Ladda station, and looted the material. They had filled the looted items in sacks and were loading it in vehicles, when caught," said Inspector In-Charge of Rayagada police station, Tapan Mohanty.
The stolen alumina powder weighed about 22 tonnes, a senior Railway Protection Force (RPF) official said.
Possible involvement of any railway officials in the robbery is under investigation and details will be known once the inquiry is over, he said.