"What we can say at this point is that an investigation is underway and we do not usually make statements until investigations are completed," Green Cargo spokesperson Lena Bjerkesjö told news agency TT. She added that an investigation can take "a few weeks".
Speaking to TT, Swedish Transport Administration spokesman Thomas Pihl said the ammonium nitrate is "a dangerous good but there is no danger to the public".
An initial inspection was carried out on the defunct train Friday evening and another was scheduled for Saturday. The Transport Administration said repairs could take a week and that the train derailed after running a red light, which damaged the gears.
Thomas Andersson of the Transport Administration told TT that the train driver had contacted the traffic control centre about a suspected break damage before the accident happened.
On Saturday, replacement buses covered some of the affected routes as train traffic came to a standstill between the towns of Eskilstuna and Västerås as well as between Eskilstuna and Arboga.
Passengers travelling from other stations around central Sweden could also be affected, the Transport Administration said, listing Katrineholm, Linköping, Norrköping and Örebro as towns where train traffic could be disrupted. "Departure times could change," said Pihl.
On Saturday, national rail operator SJ confirmed this information, but did not offer its own predictions for when train traffic could resume to normal schedules.