A ‘Mayday’ call suggesting a technical or mechanical failure on the army helicopter that crashed in Arunachal Pradesh on Friday will form the focus of the Court of Inquiry constituted to investigate the incident, officials said. The advanced light helicopter (ALH), a HAL Rudra built by Hindustan Aeronautics Limited and also known as ALH-WSI, with five personnel onboard, crashed around Migging in Upper Siang district at 10.43 am. The chopper had taken off from Likabali in the Lower Siang district.

READ | India successfully test fires Agni Prime ballistic missile off Odisha coast

Joint search operations with teams from the army and air force were launched immediately after locating the crash site, which was very remote and extremely challenging in terms of hills with steep gradients and thick jungle. While the search and rescue team retrieved the mortal remains of four personnel by late Friday night, search for one member of the security force was underway.

Public Relations Officer (Defence), Tezpur, said in a statement that the pilots had more than 600 combined flying hours on the Advance Light Helicopter (Weapon Systems Integrated) and over 1800 service flying hours between them.

READ | Congress Presidential Polls: Mallikarjun Kharge sweeps polls with 7,897 votes to Shashi Tharoor’s 1,072

“Prior to the crash, the Air Traffic Control (ATC) had received a MAY DAY call suggesting a technical or mechanical failure,” the release said. “This will form the focus of the Court of Inquiry, which has been immediately constituted to investigate the causes of the accident.”

Names of personnel killed in the accident will be released after the next of kin are informed.

This is the second incident of an Army helicopter accident in the state this month.

READ | New airbase near India-Pak will be effective centre for the country's security: PM Modi