The incident took place when the labourers were digging earth at the basement of the under-construction complex near Bais Godam area around 3 pm, they said.
"All six labourers were pulled out and rushed to the SMS Hospital where they were declared brought dead," SHO of Ashok Nagar Police Station Harsh Raj Singh told PTI.
The bodies were moved to the mortuary for identification and postmortem, the SHO said.
A case was lodged against the owner, contractor and builder of the complex and police were looking for them, he said.