At Srivaikuntam railway station, rope and accessories needed to lift people were lowered from the chopper and a number of passengers, including a boy, were airlifted to safety
"The work has commenced, passengers are being rescued," a Southern Railway official said here.
All arrangements are in place including buses to take the passengers to Vanchi Maniyacchi railway station, 38 km away from Srivaikuntam. A special train will be operated to Chennai from Vanchi Maniyachchi station.
The train was stopped at Srivaikuntam railway station in Thoothukudi district due to heavy rain and flood situation.
In total, 800 passengers were stranded and of them, approximately 500 were in the Srivaikuntam railway station and about 300 took shelter in a nearby school, a railway official said.
Heavy rain has paralysed several parts of India's southern state of Tamil Nadu, inundating roads, affecting train services, and leaving authorities scrambling to rescue those stranded.
The deluge occurred while the state was still recovering from the damage caused by Cyclone Michaung, which lashed the coast this month, killing at least 13 people.
Tamil Nadu received almost 50 mm of rainfall between Sunday and Monday, compared with the 2.5 mm that would be normal at this time of year, the weather department said, and more rainfall is predicted on Tuesday.
Local media reported at least five people died in the flooding and accidents related to the rain, which primarily affected the districts of Tuticorin, Tirunelveli, Tenkasi and Kanyakumari.
Entire neighbourhoods remained submerged on Tuesday, with houses appearing like lonely islands surrounded by murky, brown water, according to footage from Indian news agency ANI, in which Reuters has a minority stake.
Teams were using inflatable rafts to rescue people from houses and temples, and to distribute food packets to those they were unable to move to safety.
P. Veeramanikandan, a resident of Tirunelveli, who was among the volunteers working with authorities in the rescue efforts, said some areas were still too dangerous to reach.
"Areas lying closer to riverbanks are still badly affected, while water levels in other areas are starting to recede," he said.
About 500 passengers travelling to the capital Chennai remained stranded at a station on Tuesday afternoon, over 36 hours after their train was terminated early due to suspension of rail services in the region, local media reported.
The state government blamed the chaos on "record rain", which they said was the highest in six decades, coupled with the fact that it was heavier than forecast and that the warning had also been received "a bit late".
Chief Minister MK Stalin said at a media briefing the state had taken 12,653 people to 141 relief camps with food, water, medicines and essentials. Food is also being distributed using helicopters.
Tamil Nadu is no stranger to floods. Eight years ago, its capital city of Chennai was battered by heavy rains that inundated large sections of the city and killed around 290 people.