The health of the castaway who claims he spent more than a year adrift in the Pacific has deteriorated, delaying his repatriation.
Jose Salvador Alvarenga has returned to hospital in the Marshall Islands, where he was found a week ago.
Mr Alvarenga said he left Mexico for a trip in a fibre-glass boat in December 2012 with a friend who died on board.
The family of his younger friend say they want to speak to Mr Alvarenga to find out more about how their son died.
Doctors at Majuro Hospital in the Marshall Islands' capital said Mr Alvarenga was too dehydrated to travel.
"We must consider his health, that he is fit to travel, and get the doctor's recommendation. We're hoping in the next three or four days," said Mexican embassy official Christian Clay Mendoza.
Mr Alvarenga made a brief public appearance on Thursday, and correspondents say he looked weaker than when he made his first media appearance on Monday.
An unnamed official told AP that he looked much less animated.
"He looked exhausted, frankly. Like someone who has run two or three marathons."
He was rescued on Thursday by people living on the island of Ebon Atoll.
Mr Alvarenga apparently survived the 8,000 km (5,000-mile) ordeal by catching fish, birds and turtles with his bare hands.
For fluids, he claimed to have drunk urine, rainwater and the blood of birds.
Alvarenga's fishermen colleagues told AFP that he had always had an unusual diet.
"He wasn't picky. He ate everything" said one.
Family seek answers
The family of Mr Alvarenga's companion on the boat have also spoken out, saying they need more answers.
Known as Ezequiel, he is believed to have starved after being unable to eat raw birds and fish.
Romeo Cordova Rios, Ezequiel's brother, said that while the death was an accident, the family still wanted to speak to Mr Alvarenga.
"We want him to come here, for the government to bring him here," he said.
"The only thing we want is to know what was the last thing that he told this man and what he did with my brother's body," he added.
Three Mexican fishermen were rescued off the Marshall Islands in August 2006 after what they said was about nine months drifting across the Pacific Ocean.
They survived on rain water, seabirds and fish.
Castaways from Kiribati, to the south, frequently find land in the Marshall Islands after ordeals of weeks or months at sea in small boats.