Chief Minister Pinarayi Vijayan gave a direction to Chief Secretary V P Joy in this regard, a CMO statement said.
As directed by the Chief Minister, Pathanamthitta District Collector Divya S Iyer submitted a preliminary inquiry report with regard to the incident, it said.
Binu Soman (34), who acted as a volunteer in the drill organised to assess the disaster management agencies' preparedness to deal with floods, was seen drowning at Manimala river near Keezhvaipur on Thursday.
Though the man was rescued and admitted to a private medical college hospital in Thiruvalla by the officials, who took part in the mock drill, he later died on Thursday.
Earlier in the day, the Kerala State Human Rights Commission (KSHRC) registered a case into the tragic death and sought a report from the State Disaster Management Authority (SDMA) and the District Collector on the incident.
The case was registered based on a complaint lodged by a human rights activist.
The complainant alleged that if the rescue personnel had arrived on time, the life of the deceased man could have been saved.
The mock drill, without taking any precaution, was a gross violation of human rights and action should be taken against the officials who were responsible for the tragic death of the man, he further said in the complaint.
V K Beena Kumari, member, KSHRC, directed the head of the SDMA and the Pathanamthitta District Collector to submit an explanation report within the next 15 days after examining the circumstances that had led to the tragedy, an official statement here said.
The Commission would take further action after receiving the report, it added.
Mock drills were held at various places in Pathanamthitta district on Thursday as part of assessing the disaster management team's preparedness to deal with floods and landslides.
