A 25kmh speed limit applies to the 16.5km stretch of railway track between Clinton and Balclutha, which was reopened at 4.35pm yesterday.
The track was damaged last Friday when two coal wagons at the end of a northbound freight train derailed.
KiwiRail public affairs general manager Kevin Ramshaw said repairs took a day longer than expected because the initial assessment of the track was made without being able to see the full extent of the damage.
"We were a bit optimistic, but the crews worked hard," he said.
A train travelled over the repaired section to test the track yesterday afternoon, and the track was reopened shortly after.
The 25kmh speed restriction would not be lifted until all repairs had been completed, Mr Ramshaw said.
"I can't say exactly when that will be, but it could be for quite some time."
Repairs were expected to cost about $250,000, but it was likely to cost considerably more to lay sleepers to a standard which would enable the speed restriction to be lifted, he said.
There are on average eight train movements a day on the line. Fonterra has been able to hold, store or move goods by other means. The principal effect of the track damage has been the need to truck coal from Nightcaps, in Western Southland, to Clandeboye dairy factory in South Canterbury.
