Around 9 trekkers have been killed and 27 people have been rescued from the forest-fire in Tamil Nadu's Kurangani area.
"Nine persons are dead, while 17 of the rescued have been hospitalised and 10 did not require hospitalisation," Commissioner of Revenue Administration K Sathyagopal told reporters.
Among the dead, six were from Chennai and three from Erode, local police said.
Tamil Nadu Chief Minister Edappadi K Palaniswami on Monday ordered a probe into the incident. Speaking of stepped up rescue operations, Defence Minister Nirmala Sitharaman said an advanced light helicopter had been sent to save those trapped in the forest fire.
The trekkers, mostly students, were caught in a massive forest fire in Theni district of Tamil Nadu on Sunday evening. The Indian Air Force (IAF) has been pressed into service for rescue operations.
The incident happened when the students were climbing down the hills from Munnar in Kerala to Theni when they got trapped in the forest fire. The expedition was organised by a Chennai-based trekking club, which had not taken permission from the forest department.
The defence ministry swung into full force by fielding 16 commandos of the Garud Commando Force and four choppers from the Indian Air Force to fasten the rescue operation of those stuck in Kurangani forest fire in Theni district.
Meanwhile, Chief Minister K Palaniswami is rushing to Theni to oversee rescue operations.
Kurangani-Kozhukumalai hills in the Western Ghats are located near Bodinayakanur, about 40 kms from here.