Police were informed that three boys as young as ten were offering to sell their bodies to women in Norrköping.
A woman called the police on Tuesday after one of the boys approached her and offered to sell sex The children then went on to approach other women arriving at the travel hub at around 9am, the woman told police.
"The worst case scenario is that we're looking at a suspect crime such as procurement (koppleri)," Östergötland County police spokesman Thomas Agnevik told The Local.
The boys had disappeared once the police arrived at the scene, but later in the day one of them was seen begging at another location. He was taken in by the police, but released and later that day made his way back to the transport hub Resecentrum to ask for money from passers-by. The police took him in a second time and turned him over to social services.
Social workers later handed the boy back to his parents.
"That boy has been spotted by himself twice, which is very serious," police duty officer Tor Sevelius told The Local on Wednesday.
He said that the number of incidents of begging had risen in Norrköping, but not until recently had they begun to receive reports of children out by themselves without an adult. The boy who ran into trouble twice on Wednesday was a Romanian citizen, the police confirmed.
The Tuesday morning phone call was the first report of young new arrivals trying to sell sex.
"These are children from other countries, they don't know the language, and they are very vulnerable," Sevelius said.
He explained that Swedish police cannot interrogate children younger than 15, and they had not spoken informally with the boy before handing him over to social workers.
Social workers told the police that if the boy was found walking the streets alone again, the authorities may consider taking him into care.
"The parents were told that it's not OK to let children walk around begging," said Agnevik. "Either we have a really bad situation where parents are sending out their kids to beg for money, or we have an even worse situation where they are out trying to sell sexual services."
The report of soliciting came from just the one witness, whom the police were trying to reach for further information on Wednesday morning. No further witnesses from the travel hub had come forward.
"We have no reason not to believe her, but as we don't have any further information at the moment the investigation is at a standstill," Sevelius told The Local. Agnevik said that the Östergötland police had not received any reports of temporary camps, such as the suburban shantytowns that have sprouted around Stockholm.
In nearby Linköping, the municipality and the local Ryttargårdskyrkan church have joined forced to offer lodgings and some food for unemployed Europeans who have travelled to Sweden.
"We try to practice what it says in the New Testament, and it says 'Help homeless people', full stop," pastor Eleonore Gustafsson told The Local, adding that most people who slept in the church were Bulgarian or Romanian.
"It's short-term help to make sure they have a roof over their heads, which is why we work with the (homelessness organization) Stadsmissionen for more long-term solutions," she said, adding that the Swedish evangelical churches also did a degree of outreach work in vulnerable communities across Europe.
Back in Norrköping, one woman who contacted the police told them that that a young boy, also speaking German, had knocked on her door asking for food.