An Auckland District Health Board spokesman said the woman, aged in her mid-40s, was in a stable condition at Auckland City Hospital.
Her 7-year-old daughter, also in a stable condition, was admitted to Starship Hospital.
Their conditions were downgraded after earlier reports listed them as being seriously injured. The other two girls were not admitted, he said.
KiwiRail confirmed the train was one of its freight trains, travelling northbound from Auckland to Whangarei. The train driver was not injured.
There is no barrier at that level crossing, however, lights were flashing and bells were ringing at the time of the collision, the KiwiRail spokeswoman said. A witness also confirmed this to police.
The Waitemata police serious crash unit was investigating the collision in conjunction with KiwiRail.
The company said there are 1330 public road level crossings nationwide and 110 stand-alone public pedestrian level crossings.
Of the road level crossings, 278 were protected by barriers, flashing lights and bells, 423 were protected by flashing lights and bells and the remaining 629 crossings were protected by passive signs.
A large number of rail crossings also existed on private land, and it was not KiwiRail's responsibility to upgrade their safety features, the spokeswoman said.
KiwiRail held a priority list of upgrades to public road level crossings, she said.
"In order to prioritise crossings for upgrading safety measures, we rank them according to a number of factors, including the volume of road and rail traffic, the road layout [and] sight lines.
"After an incident at any level crossing, we'll reassess it just to determine if the current safety measures are appropriate, or if the crossing needs to be given a higher ranking," the spokeswoman said.
"We urge all motorists at all times to approach all level crossings with care and to heed the warning signs and alarms.
"If are bells are going of and the lights are going off, it means stop."
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In the past 12 months:
- 20 people have died in level crossing incidents. The figure includes suicides.
- 154 have been injured at level crossings
In the past 10 years:
- More than 240 cars have collided with trains at public road level crossings in New Zealand.