The cause of the derailment was still being investigated.
The Hawke's Bay line has been closed north of Napier for six years but is due to reopen all the way to Wairoa.
A railways enthusiasts' steam train is also scheduled to run north as far as Napier early next month.
The Labour-led coalition earlier this year announced a $5m contribution from the Provincial Growth Fund to reopen the line north of Napier for logging trains to relieve pressure on the highways, with work starting almost immediately on reinstating the track to take an estimated 6000 truck trips off the highways.
Originally, KiwiRail expected to complete work to get logging trains moving again between Wairoa and Napier by the end of the year but a washout caused by a storm last month ruined a 45-metre section of track just north of Raupunga. KiwiRail has since not been able to commit to a date for the reopening of the line, and is still assessing the problem.
"We are working our way through a number of potential scenarios for repairing the damage caused by the slip at Raupunga on the Napier-Wairoa line before deciding on a preferred option," Clarke said.