The number of teenagers being used by the drugs trade in south Wales is rising and it would be "naive" to think none are from the area, a senior police officer has said.
Drugs gangs often use youngsters from outside an area to deal drugs.
This week a man was jailed for bringing an orphan from London to deal heroin and crack cocaine in Swansea.
South Wales Police Det Insp Stuart Johnson said more children are being used in Swansea and Neath Port Talbot.
"What we tend to find is the use of children who have come from other forces - usually London, Birmingham and Liverpool," said Mr Johnson, who covers the area.
"The scale of the children being used locally is something we're working on and trying to develop.
"We'd be very naive to think we haven't got [local] children being used.
"It is increasing. We've had children as young as 13 in Swansea and Neath Port Talbot on quite a regular basis.
"But what we need is information from the public, from parents, from schools and friends to say what exactly is the scale of the problem."
Mr Johnson said young people were a "disposable commodity" to dealers because if they were caught they were likely to get a lenient sentence because of their age.
Swansea and Neath Port Talbot are in the top 10 for heroin deaths in England and Wales.
What is county lines?
County lines sees urban gangs from the likes of London, Liverpool and Birmingham introduce an untraceable phone number in a different area to sell crack cocaine and heroin directly at street level.
Local runners - often teenagers - then supply the drugs in these suburban areas, market towns and coastal towns around the UK.
The gang often exploits young or vulnerable people to provide locations for drugs to be stored in these new areas, known as cuckooing.
They had more than 4.5 deaths from the drug and morphine per 100,000 people between 2014 and 2016.
Jamie Harris, service manager at drugs charity Barod, said Swansea had seen the "harder end" of county lines.
"Swansea is quite unique in that we've never really had gangs who are native to the Swansea area," he said.
"We've seen gangs working side by side without any impact on their sales but how long that can continue for I'm not sure.
"Some of the exploitation we've seen in the Swansea area is from young people being used to transport drugs who are not from the Swansea area right through to local young people being used to distributing drugs, even to the point where they're being sexually exploited.
Dr Mohammed Qasim, a researcher with ethnic minority gangs, has studied the situation in Swansea but said it was not suffering on its own.
He added: "It's an issue that seems to have got worse in recent times. We have these gangs coming and basing themselves in Swansea.
"The gangs from London tend to use children from their areas and that's based on trust and access.
"Local drug dealers will try to get local kids on drugs and through that process, exploit them.
"This is not something that's going away."