Majuro, Marshall Islands (CNN) -- Jose Salvador Alvarenga, the mysterious castaway who turned up in the Marshall Islands last week, has been released from a hospital.
He had been readmitted Thursday amid concerns that his health was deteriorating. Doctors reported that he was severely dehydrated, running low on vitamins and suffering from swollen legs.
Alvarenga, whose tale of surviving 13 months adrift in the Pacific Ocean has prompted fascination and skepticism, left the hospital Friday and is now staying at a hotel in Majuro, the capital of the island chain.
Hospital officials didn't provide an update on his condition. But Dr. Franklin House, a retired American medic working at the hospital who has spent time with Alvarenga, said he was concerned about the state of the castaway's kidneys.
Alvarenga, an El Salvadoran who had been living in Mexico before he got lost at sea, washed ashore in the Marshall Islands more than a week ago. Earlier this week, his condition improved enough for him to be released from the hospital.
But after his health took a turn for the worse Thursday, plans for his repatriation to El Salvador have now been postponed.
House, who is not Alvarenga's treating physician, said the castaway had complained to him of kidney pain since his arrival at the hospital.
The 78-year-old doctor, who speaks Spanish, said he suspects that Alvarenga is suffering from scurvy as a result of his poor diet and that edemas are causing the swelling and pain in his legs.
Alvarenga has said that he survived during his months at sea by eating raw fish and turtles. He says he relied on rainwater and urine for fluids.
When the doctor spoke with the castaway, he noticed that his fingers were stiff and he moved his hands slowly. Alvarenga complained of pain in his joints, knees and ankles, House said.
The first time House saw Alvarenga in the emergency room, his legs were hard and his skin was leathery. But when he returned to the hospital this week, his legs had changed to swollen, and his skin was tender and red, he said.
The doctor's assumption is that the castaway is recovering, but that it is a process that will take weeks, not days.
House also believes that Alvarenga is suffering from post-traumatic stress disorder.
Official: His story is probable
Alvarenga's claims have garnered widespread skepticism about how he could survive for 13 months adrift in the Pacific. But from what officials can tell, they have no reason to doubt him.
"The investigations into Mr. Alvarenga's story so far have been substantiated," Phillip Muller, the Marshall Islands' foreign affairs minister, said Thursday.
Christian Clay-Mendoza, a Mexican diplomat working on Alvarenga's case, said that the castaway was an undocumented worker in Mexico, but that "what he has said to us about his identity, so far, has been true."
"The main question now is how long was he at sea," he said.
Clay-Mendoza said "it's probable" that Alvarenga did get lost at sea starting in December 2012, as the castaway has claimed.
If Alvarenga's story proves true, the trip across the Pacific would have taken him across roughly 6,600 miles (10,800 kilometers) of open ocean before ending in the Marshall Islands, about halfway between Hawaii and Australia, in the northern Pacific.
The other man
Alvarenga says he set off on a fishing trip from the port of Paredon Viejo, Mexico, near the southern coastal city of Tonala.
He said he and another man intended to spend a day trying to catch sharks, but they were blown off course by winds and then got caught in a storm, eventually losing use of their engines.
Bellarmino Rodriguez Beyz, the owner of Alvarenga's boat in Mexico, identified the fishing partner as 23-year-old Ezequiel Cordova.
Alvarenga said that four weeks into their drift, his companion died of starvation because he refused to eat raw birds and turtles. Eventually, he threw the body overboard.
"What else could I do?" Alvarenga said.
A grieving family
Back in the Mexican village of El Fortin, Cordova's family is inconsolable. More than a year after the young man went missing, his mother is grieving his death.
"The pain is so great, I can't explain it," Cordova's mother said. "Losing a child is the hardest thing to bear in life."
Cordova's brother said the 23-year-old took care of his family -- and that's why he became a fisherman, in hopes of earning a better livelihood.
"My brother was kind, he was responsible for my mother," he said. "In fact, he worked in the sea because of her. He wanted to improve himself. He didn't want to be poor, like us."
Now that Cordova's mother knows her son is dead, she wants answers.
"As a mother, I demand the authorities allow me to talk to the survivor," she said. "Only in that way will I know what happened, and what he did with the body of my son. I deserve to know the truth. "
Suzanne Chutaro and Jack Niedenthal reported from Majuro, Marshall Islands; Jethro Mullen reported and wrote from Hong Kong. CNN's Holly Yan and Nick Parker also contributed to this report.