Maersk Line has brought in salvors Smit and Arden to extinguish the fire on its Maersk Honam off India's Lakshadweep Islands.
The Danish company said the Indian Coast Guard started firefighting on Thursday with one ship.
The first two specialised firefighting vessels arrived on Friday morning and have begun tackling the flames.
Maersk has sent two technical engineers to Salalah, Oman, to work closely with Smit and Ardent.
