The hunt was on Tuesday for a 12-year-old Swedish boy who's been missing since he was spotted leaving a hospital in post-tsunami Thailand with an unidentified man.
Swedish and Thai police were jointly conducting the search effort for the adolescent, Kristian Walker (search), who was apparently last seen Monday with an unknown German man at a hospital near the resort of Khao Lak (search).
The pair left the facility in the wake of the Christmas weekend tsunami disaster that has ravaged much of south Asia, including vacation spots in Thailand. A boy matching Kristian's description was seen with the man, but the child has since vanished, seemingly without a trace.
His American grandfather, Daniel Walker, and his father, Dan Walker, are involved in the desperate search to find the missing child.
Swedish and Thai police said they were searching for the boy, but said they could not confirm media reports that he had been kidnapped. The boy was listed as missing by international law enforcement agencies worldwide Tuesday.
There is growing concern about the exploitation — sexual and otherwise — of children orphaned or lost in the wake of the earthquake and storm that leveled much of south Asia, has taken close to 150,000 lives and left at least 5 million people homeless.
"There’s an element of this world that prey upon children and this is a particularly easy time for them where they can prey upon the weak, the vulnerable and the needy," Pete Banks of the National Center for Missing and Exploited Children told FOX News on Tuesday.
Reports surfaced Tuesday of children being snatched and then sold as they wandered around after the tsunami.
"This has happened in the past before this devastation, and now with the devastation it makes it that much easier to perpetrate these crimes," Banks told FOX News.
Two Swedish police officers were assisting in the investigation to find Kristian, National Police spokeswoman Carolina Ekeus said.
Dr. Pisith Yongyuth, director of Taimuang hospital in Phang Nga province, told the AP that a German man brought a boy who might be Kristian to the hospital around 1 a.m. on Dec. 27 — the day after the tsunami hit — accompanied by another boy about 8 years old. By late morning, all three had left.
"We cannot confirm that this boy is really Kristian Walker; we can only say that he seems to be the boy described by his grandfather and media reports," Yongyuth said.
While he acknowledged that his son may have already been taken out of Thailand, Dan Walker said he has urged Thai authorities to send Kristian's picture to all border patrols and airports to help prevent him from leaving the country.
The Swedish tabloid Expressen and other media reported on their Web sites or in Tuesday's editions that police were searching for Kristian amid fears he was kidnapped. Expressen said the boy was accompanied at a hospital by a man described by employees as "European looking, with a moustache and red shirt."
In the wake of the devastating tsunami, there have been unconfirmed reports of dozens of orphaned children being taken by unidentified people, some of them possibly child traffickers.
Thai Foreign Minister Surakiart Sathirathai (search) said Tuesday the Thai government was working closely with hospitals to prevent human trafficking gangs from taking advantage of the situation, although he stressed that there was no firm indication that they were.
Asked about the possible exploitation of children, U.N. refugee chief Ruud Lubbers told a cable news channel: "We are prepared for this ill behavior. ... We are cautious."
This week, the Swedish branch of Save the Children (search), or Raedda Barnen, warned governments in south Asia to be mindful of children left orphaned or without families in the disaster, saying they could be potential targets for pedophiles.
"The experience from other catastrophes is that children are particularly vulnerable," said Charlotte Petri Gornitzka, managing director of the agency.
Dan Walker said he was fearful that his son may have fallen prey to pedophiles that have been known to gather in Thailand, or child trafficking rings, but he was not sure.
"I can only guess, and you can only guess, what has happened to him," Walker told The Associated Press.
Thai Police Lt. Col. Preecha Kraewthanong said they were checking border points to see whether the boy and the man had left.
"We are looking for him to be sure whether he kidnapped the boy or not and the boy was really Kristian Walker or not," he said.
Kristian's father said two doctors at the hospital identified his son from photographs that were shown to them by Daniel Walker last week.
Both men had gone to Phuket after the tsunami to search for their family, which was on vacation with Dan Walker's estranged wife, Madeleine, who is still missing. Dan Walker's two other children, David, 14, and Anna, 7, were found and are back home in Sweden with him.
Daniel Walker, a trained paramedic and former U.S. Marine, has remained in Thailand to search for his grandson.
While Kristian's name does not appear in any hospital records, Dan Walker said his father is convinced hospital officials are correct.
"To me, that's enough to keep searching," he said.
Dan Walker said Kristian speaks English but it was unclear whether the boy in the hospital had talked to the man he left with. If Kristian did leave willingly with another man, he must have won his trust, Dan Walker said.
"I assume that he wasn't drugged or in a state of shock," he said.
FOX News' David Asman, Catherine Donaldson-Evans and The Associated Press contributed to this report.