It is inter-city trains between Stockholm and Västerås, Gothenburg and Örebro that are affected, by the closure of the stretch between Bålsta and Enköping.
So far there is no news of when trains will be going again, reports news agency TT.
The Traffic Administration says it would be dangerous to run trains past the stretch where the electricity cables have been stripped of copper.
So far the Administration cannot say how much copper has been stolen. "All that is needed is from someone to take an essential line, and electricity can be conducted to the wrong things," says spokesman Roger Falk at the Traffic Administration, to TT.