All dignitaries, including Mahajan, Naidu and Chouhan who were present on the dais, are safe, Additional District Magistrate (ADM) Ajay Dev Sharma told PTI.
The pandal was erected for 'Pranam Indore' programme which was organised this evening to thank people in view of Indore being declared as the cleanest city in the country under the recent 'Swachh survekshan 2017'.
The ADM said four persons sustained serious injuries to chest and head in the incident and were admitted to ICU of a hospital here. There condition is stable now, he added.
While power supply got snapped, scared people started running helter-skelter, they said, adding rains caused water- logging at the venue.
The chief minister personally monitored the rescue work at the spot and directed officials to rush the injured persons to hospital.
"All the dignitaries including Naidu and Mahajan are safe," Chouhan later said in a tweet.