In a freak accident, a 1000-tonne freight train crashed into and ripped apart tractor being driven by a girl in her teens, who is now in critical condition after the tragic incident Saturday morning.

Jennifer Hughes, 19, was helping her father Paul Hughes with haymaking while her father manned another machine. Her father saw how the train clipped the back wheel of the tractor she was driving, when he looked after hearing the sound of the train's horn.

When emergency services arrived at the scene, the tractor was seen mangled and ripped in two.

Ms Hughes was towing a hay rake across the track where it runs through the farm.

Palmerston North rescue helicopter flew Ms Hughes to hospital, where she is hoped to recover from critical head and chest injuries.

Feilding Sergeant Grant Lawton said the accident was uncommon in nature, and investigation was still ongoing.

"It's not something she will want to remember if she wakes up," he said of the tragic incident, noting the crossing was uncontrolled, without bells or barriers.

Kimberley Brady told Dominion Post train services were delayed while the accident scene was cleared and the driver was immediately stood down.