An investigation has been launched into what caused a steam train to start 21 fires spread over 12km south of Oamaru, Dunedin Railways operations manager Grant Craig has confirmed.
Mr Craig said the company had planned carefully before taking the coal-fired steam locomotive on a return trip from Dunedin to Oamaru on Saturday.
''We wouldn't have run the excursion if there were any big issues. We consulted with the Rural Fire Office, we put a lot of mitigations in place to stop fires, like diesel engines on and a 60,000-litre water tanker on the back, and we thought we had it all covered,'' he said.
The engine ran without a problem in the morning from Dunedin to Oamaru.
''That's where the steep grades are and we had no problems on the way up, so something odd has happened on the way home,'' Mr Craig said yesterday.
He said he would be compiling reports from all of the staff involved.
''It was run under our licence. It was purely a Dunedin Railways service and we had to have all of the mitigations and things for running, just like KiwiRail do, and that's what we did for this service,'' he said.
''There are a whole lot of insurance issues we've got to deal with.''
Otago Rural Fire Authority principal rural fire officer Stephanie Rotarangi confirmed they had worked with Dunedin Railways to ensure precautions were taken, as conditions in North Otago were very dry.
''The cause of the fire is still under investigation ... We're still not quite sure what happened,'' she said.
The locomotive had been hired from Mainline Steam Heritage Trust, after it was brought to Dunedin for the filming of Light Between Oceans last year.
The 400-passenger train had left Oamaru Railway Station at 2.15pm, but did not arrive back in Dunedin until about 6.45pm.
The drivers stopped in Maheno and waited for Fire Service clearance before carrying on to Herbert, where a diesel unit was added to haul the train to Dunedin, Mr Craig said.
Efforts by firefighters from Glenavy to Palmerston to extinguish the 21 fires continued from 2.30pm on Saturday into early yesterday, as two more fire calls came in overnight.
''There were dozens of spot fires burning [overnight],'' Otago Rural Fire Authority rural fire officer Eric Spittal said.
Railways staff also patrolled the stretch overnight, stopping one train at Herbert, while fire crews attended to fire threatening a barley paddock about midnight.
Another fire flared up about 3am between Fortification and Thousand Acre Rds.
Speed limits remained for trains along the 12km stretch and the Rural Fire Office was on ''full alert'' yesterday.
Mr Spittal said it had been an ''astonishing event'' and he heaped praise on the firefighters, Central South Island Helicopters and the community for their help.
''It was an amazing save all round from everybody,'' he said.
Because of the quick action, the damage was limited.
''But it is still going to be a very expensive fire.
''There's a lot of damage to fences, a lot of damage to pasture, a lot of individual damages to property,'' he said.
Central South Island Helicopters director and pilot John Oakes said it was ''quite phenomenal'' how much water was needed.
Its B3 Squirrel dropped 85,000 litres in 85 separate 1000-litre loads, a BA Squirrel dropped 81,500 litres in more than 115 700-litre loads and a McDonnell Douglas 520N dropped 60,000 litres in 120 500-litre loads between 2.30pm and 9.30pm on Saturday, making more than 310 drops.
The water was pulled out of the Kakanui River and irrigation run-off ponds along the railway line.
''They [irrigation ponds] are really valuable at times like this,'' he said.
Federated Farmers North Otago president Richard Strowger said the weekend's events were ''a healthy reminder of how careful we have to be'' in such extreme dry conditions''.
Totara farmer Jock Webster took part in ground efforts to control the fires near his property and said it was ''lucky'' to have happened while crops were still green.
''Crops are still just green enough and fortunately it wasn't that windy and that wildly hot [on Saturday],'' he said.
''It was just lucky it was not two weeks later, or it would've been a very serious issue.''
Mr Webster was yesterday running an irrigator along the railway line.
''You get clumps of grass and it gets so hot underneath them, smouldering away, and I wouldn't want it to flare up in another two weeks,'' he said.
