The injured were taken from Kengari, about 20 km from here, to a state-run hospital.
"The rescue operation is on to find if more workers are still trapped under the debris as the supporting walls also collapsed under the impact of the crash," Ramaswamy said.
A religious institution was building a three-floor wedding hall at the site, where work was hampered due to heavy rain in the last two days.
"Police have registered a case against the building contractor and are investigating to ascertain if any spurious material was used for construction," Ramaswamy said.
Home Minister K.J. George and officials visited the incident site.