A number of spot fires broke out along a railway line between Aylesbury and Darfield, west of Christchurch and were first reported about 4.30pm Sunday.
By 7:30pm Fire and Emergency (FENZ) confirmed that houses in the area, and especially near Kirwee, were "no longer ... under immediate threat from fire", and no homes had been damaged.
However three helicopters were still at work on the hotspots, along with 17 ground crews, using pumps, tankers, smoke chasers and a Command Unit.
People were initially asked to keep away from the area, with police working on setting up road closures, but State Highway 73 would be reopened soon, FENZ said.
One of the blazes was believed to have started by sparks from a train travelling toward Darfield, and the fire crews had been working on multiple blazes at once.
"A freight train shunting wagons from a milk factory in West Rolleston was held back near Darfield earlier today after it created a number of grass fires along the track," a KiwiRail spokesperson said.
"The train was stopped while the incident was being investigated. No one was hurt."
KiwiRail said affected services overnight include the TranzAlpine travelling from Greymouth to Christchurch with 172 passengers on board. Overnight freight services are also affected.
Bus replacements are in place for the TranzAlpine passengers.
"We are sorry for the inconvenience, but safety has to be our top priority," the spokesperson said.
Kirwee township resident Pauline Hubbard, who lives near the railway line, said the fire began moments after a train went past.
"It had six locomotives pulling the train, and it was soon after that the fire started. And apparently - my daughter's just rung me, and she said there were sparks coming out from the locomotives."
Hubbard said it was not the first time a train had caused a fire in the area.
An RNZ reporter at the scene said the police have lifted a cordon which was set up at the intersection of West Coast Road and Courtenay Road.
