The incident took place this afternoon at the under-construction Zila Panchayat building in Dharampura area while labourers were working there, Mungeli Superintendent of Police Neethu Kamal told PTI.
A portion of the slab which was being laid fell down on the labourers. Police personnel were rushed to the spot along with rescue team, she said.
"So far four out of five labourers who were trapped inside the rubble have been evacuated and admitted to a local hospital where their condition was stated to be out of danger," the officer said, adding efforts are on to rescue another trapped worker.