The fire broke out near an oil pipeline in the Gulf coast state of Tabasco on Dec 22.
The Tabasco Health Department said yesterday that the latest death was a 33-year-old man who died on Sunday after suffering third-degree burns over three-quarters of his body.
Two injured men remain in stable condition.
The state-owned oil company, Petroleos Mexicanos, said the fire ignited in a pool of fuel left by thieves after they drilled a tap into a pipeline.