Fifteen young refugees have gone missing from care in Leicestershire in the past 10 months.

Council staff fear some may have been picked up for illegal employment in the drugs or sex trade.

Three have been found in other parts of the country, but 12 remain missing.

One of the missing children was found recently after a raid at a cannabis factory in the north of England, council bosses said.

The other two were found after being seen outside the county.

The missing youngsters are asylum seekers from countries such as China, Afghanistan and Vietnam.

The children had been dumped by the side of main roads or left at places such as Leicester Forest East services or East Midlands Airport. They were given places in care homes and foster homes. Until they are 18, any vulnerable foreign national is looked after by the council in charge of the area in which they are found.

A Leicestershire County Council spokesman said: "Some of these young people go missing because they have arrived in the wrong area. They leave to try to get somewhere else or find relatives. Most will go missing within the first three to seven days.

"There are concerns that some of the youngsters could be trafficked into the country for illegal employment, which could include the drugs or sex trade.

"The youngsters may have an arrangement to contact someone when they arrive and are picked up.

"We offer a safe and secure environment for children but we cannot keep them locked away so a minority will use this opportunity to leave."

The spokesman said that while 15 have gone missing, nearly 100 similar children are happily living in Leicestershire's care homes or with foster families.

When a child goes missing the authorities contact the police and carry out a risk assessment to see if they can work out where they may have headed.

Missing persons' agencies are also contacted to help distribute photographs to other authorities and carry out poster campaigns in other towns or cities.

In the city, no children are missing permanently.

A spokesman said: "In the six months from March to September, 2008, 21 children who live in children's homes have been reported missing to the police.

"Analysis of the statistics shows that about 90 per cent of young people return to the home within 24 hours. Often the young people will have gone to stay with family or friends without permission.

"We know who is missing from our care.

"We have well-established, stringent procedures in place to deal with this issue.

"We work very closely with the police, and we work tirelessly to ensure that children return to our homes and are safe."