Faridabad deputy commissioner Balraj Singh, DCP Raj Kumar Vaishishta and minister for labour Shiv Charan Sharma also rushed to the spot.
Rajesh Gupta, a resident of Jawahar colony, was constructing the industrial unit in Saroorpur. On Saturday, the labourers under the guidance of contractor Gyanshyam Khanna were laying lintel on the 7,000 square feet area on the first floor, police said.
As a major part of the floor collapsed, the contractor and six workers were trapped under the rubble. Some of them were pulled out and rushed to BK Hospital. The contractor was one of the dead persons. Another labourer named Sipoy was declared dead in the hospital later. Three other injured workers are undergoing treatment at the hospital.
The authorities are investigating whether the owner had permission to construct the industrial unit.
"The rescue work is on and all efforts are being made to ensure that no one is under the debris," deputy commissioner Balraj Singh said.