"IndiGo flight (6E-523) departed from Chennai, with 163 passengers and six crew members, as per schedule at 8.10 am but had to land back at the airport at 8:33 am after smoke alarm of the cargo hold area went off," an airline spokesperson said in Delhi.
Keeping in mind passenger's safety, the Captain alerted the air traffic controllers at the Chennai airport which declared an emergency and fire tenders and ambulances were kept ready.
The plane, an Airbus 320, landed safely and the passengers were deboarded, the spokesperson said.
Before landing, the pilot also switched on the Electronic Centralised Aircraft Monitoring system (ECAM), which activated the fire extinguishers in the cargo area.
All 163 passengers were later accommodated on an alternate IndiGo flight.
"There was no actual fire or smoke - it was only a warning alarm. The aircraft has been grounded for further inspection at the Chennai airport," the spokesperson said.
Airline officials said electrical wiring, computers and other aspects were being checked to ascertain why the warning alarm went off.