Aside from search work, rescuers have been tasked with providing communication support and disinfecting personnel and facilities involved in the mission, he said.

They have also helped investigators drain water from areas near the main crash site, he noted. Monitoring for flammable gas has been carried out regularly.

The steep and densely vegetated terrain near the main impact point has posed some challenges to his team as they enlarged the scope of the search on Thursday, he said.

Firefighters have to carve their way through with shovels and sometimes climb over big stones to proceed, he said. They are also often troubled by snakes and insects after heavy rainfall.