Southern regional manager Neil Campbell said railways throughout the world faced the same problem and must take measures to monitor rail temperatures to prevent any risk of track misalignment or heat buckling.
"While we regret any inconvenience to passengers travelling on our Tranz Alpine service, we cannot compromise on safety," Mr Campbell said.
Rail management in hot weather was an ongoing activity and could not be avoided, he said.
"We have been carrying out rail conditioning work, or de-stress as we describe it, for many years now to reduce the risk of buckled track in hot weather, but we can never eliminate it.
"These days we weld the rail up so that it has no rail joints, and then de-stress the rail to control expansion in the heat. There will be speed restrictions imposed where necessary to ensure the safe passage of trains," Mr Campbell said.
- The Greymouth Star