NEW DELHI, March 16 (Xinhua) -- The death toll in a forest fire in southern state of Tamil Nadu has risen to 14, with some of the critically injured trekkers succumbing to their burn injuries at the hospital in the past 24 hours, police said Friday.

The massive fire broke out late Sunday evening when a group of nearly 40 people, mostly college students, went trekking in Kurangini hills in Tamil Nadu's Theni district, some 540 km from the state capital of Chennai.

While 10 people - seven women and three men - initially died in the fire, 30 others were rescued by Indian Air Force. "Of those rescued, some sustained severe burns. Four of them have so far died during treatment at a government hospital," a senior police official said.

Police have already arrested a 30-year-old tour guide in connection with the fire. "The tour guide led the trekking group to the forest. He is being interrogated. Preliminary probe suggests that the trekking group did not obtain required permission from the authorities," he said.

A probe is underway to ascertain the cause of the fire.

"We will try to fix responsibility as soon as the investigation is over. Anyone guilty will not be spared," the official added.