The incident occurred between Aneby and Nässjö at 5 pm, and affected the SJ trains, among other things.
According to the police, the train never derailed and there are no reports that anyone was injured.
- It was a hydraulic tank that broke down and caused a major leak, says Johan Ragnar, internal commander at the rescue service in Jönköping.
The rescue service and the Swedish Transport Administration were on site during the evening to investigate the extent of the leak.
The work caused delays, but by 7 pm the following trains had begun to roll slowly along the route.
Replacement buses were also used for local traffic.
The police state that they must investigate the reason why the object was on the rails.
- We have no information about what it was, says Johan Ragnar to SVT.
According to SJ, their train was able to get past the site at crawl speed during the evening.
- Our high-speed trains are now rolling, but with delays, said Stefan Holmlund at SJ's press office at 20.30.
The Swedish Transport Administration's forecast is that the trains can run normally again at 5 o'clock on Friday morning.
Photo: Tobias Marbenius