UNICEF and other child welfare groups warn that the gangs - well-established in Indonesia - may well be whisking orphaned children into trafficking networks, selling them into forced labor or even sexual slavery in wealthier neighboring countries such as Malaysia and Singapore.

Such trafficking, if confirmed, would vastly deepen the suffering of children already struck hard by the Dec. 26 earthquake and tsunami. Indonesia estimates that 35,000 children on Sumatra island's Aceh province lost one or both parents to the disaster.

Fueling the suspicions, many Indonesians have received mobile phone text messages this week inviting them to adopt orphans from Aceh. The police are investigating the messages.

It's not clear whether such messages are pranks, real adoption offers or linked in some way to trafficking networks. The Associated Press was unable to get through to phone numbers given on two of the messages.

Child welfare experts warn the messages could be a sign that children are being removed from the province, reducing their chances of being reunited with relatives or surviving parents who may be searching for them.

Little Evidence

``I'm sure it's happening,'' said Birgithe Lund-Henriksen, child protection chief in UNICEF's Indonesia office. ``It's a perfect opportunity for these guys to move in.''

Officials concede that they have little hard evidence of specific cases but say the aftermath of a natural disaster is a perfect breeding ground for such traffic. Hundreds of thousands of people have been driven from their homes, children have been separated from their families and the deaths of parents leave their offspring especially vulnerable to criminals.

In Thailand, Foreign Minister Surakiart Sathirathai said Tuesday that his 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.

The threat of trafficking appears more serious in Indonesia than any of the other southern Asian nations hit by the tsunami, probably because the scale of death and destruction is greatest and the territory more remote, UNICEF Director Carol Bellamy told The Associated Press on Tuesday.

`Child Slaves'

Making matters worse, the hardest-hit area in Indonesia - Aceh - is not far from the port city of Medan and nearby island of Batam, which are well-known transit points for gangs shipping children and teenagers out of Indonesia.

``This is a situation that lends itself to this kind of exploitation,'' Bellamy said. ``Our concern here is ... whether these children are frankly turned into child slaves, if you will, or abused and exploited.''

``They could be put to work: domestic labor, sex trade, a whole series of potential abuses,'' she added.

Bellamy said it was not clear whether children already had been trafficked. She said that such smuggling did not appear to be widespread and that UNICEF and other agencies were working hard to make sure it does not become a bigger problem.

Indonesian officials were already taking steps, ordering provincial commanders, especially in and near Aceh, to be alert to possible child trafficking. Police officers in some Aceh refugee camps urged people to be skeptical of anyone claiming to be from a charitable group aiding children or saying they are related to an orphan, National police chief Gen. Da'i Bachtiar said.

Bellamy applauded the government's announcement Monday that it was temporarily barring anyone from taking Acehnese children younger than 16 out of the country.

Children must stay in Aceh until all are registered, which could take a month. After that, they will be allowed to leave.

Bellamy said registering Acehnese children was a top priority and would help reunite families.