Technicians at the Gothenburg tram operator, Göteborgs Spårvägar, GS, have initiated an investigation of the carriages involved in the accident to find out if they were faulty.
"What we do know is that the tram was at a standstill. When the driver got a green light to start he went. He then noticed that something was wrong, and people outside were yelleing and waving. He stopped immediately," Åsa Berndtson, head of communications at GS told news agency TT.
Maria Andersson, leading the internal investigation at GS, said that it seems likely that the girl had tried to climb through the gap between the two last carriages while the driver was waiting for the green light, local Göteborgsposten newspaper reported.
When the tram then started moving, the girl most likely fell down and was dragged along the tracks before a nearby driver noticed something was wrong and could signal for the tram driver to stop.
The Gothenburg police department has also started their own technical investigation, and have been talking to witnesses for clarity in how the accident could occur.
"There is currently no suspicion of crime," said Ulla Brehm with the police in the Västa Götaland district.
The girl died from her injuries at the site of the accident.