Nine people, who were part of a 36-member trekking team, were killed in the incident on Saturday.
"Without permission, they embarked on a trekking expedition. Trekkers should climb hills only after taking the government's nod," the chief minister said here.
Stern action would be taken in the future against trekkers who undertake such expeditions without the state's permission, he said.
During the summer months of March, April and May permission to trek is not given as the high forest ranges are dry with the possibility of forest fires spreading fast, he said.
The team comprised 24 people from Chennai and 12 from Tiruppur and Erode districts.
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