Police have named the two tourists who died in a crash in Selwyn on Sunday.

Fox McCrossin, 58, and her wife, Joan McCrossin, 56, from Australia died after a crash involving a truck and several other vehicles on State Highway 1 south of Christchurch.

Police were called to reports of a truck rolling about 8.50am and arrived at the scene soon after. Seven other people were injured in the accident.

The truck involved in the serious crash on State Highway 1 near Rakaia ended up off the road and near railway line. Photo / Bridget Shimmin

Photos showed that two of the vehicles had swerved off the road and onto train tracks running parallel to the highway.

At least three appliances were called to the scene.

Police have expressed their condolences to the couple’s family and friends.

An investigation into the circumstances of the crash is continuing.

Photos showed the truck - that had been pulling two trailers - having flipped and come to rest across railway tracks, shutting down the train line south of Christchurch.

• Two dead, seven injured in Canterbury crash

A resident of a local farm said he heard a bang and went out to see what had happened. He could only see the truck - no cars were visible from his farm's boundary.

The crash happened right on the Main South Rd bend, he said.

Bridget Shimmin was on a southbound Intercity bus that arrived on the scene not long after the crash.

She said a car that was involved in the crash had ended up at least 100m down the road.

"[It] sounds like the truck clipped the car and spun out of control as a result. I think a couple of other cars closely missed the truck and had to swerve out the way."

The bus had waited at the scene while several paramedics who happened to be on board went to help, Shimmin said.

Once they reboarded the bus was redirected onto a gravel road that looped back to SH1 just before Rakaia.

St John was called at 8.45am, and five ambulances and a helicopter were sent to crash, a spokeswoman said.

Three fire appliances from Rakaia and Dunsandel were also in attendance.