The Pacific National freight train reportedly collided with a truck on the Barrier Highway at Bindarrah about 10.30am local time on Sunday.
A spokesperson for the company confirmed two of its Port Augusta train crew were killed in the crash.
"Pacific National takes the safety of its employees very seriously and has notified regulators who are investigating," the spokesperson said in a statement.
"This incident is having a profound impact across the organisation, and our first priority is to ensure the highest level of care to the families of our drivers who have tragically died."
Motorists travelling between NSW and South Australia are facing heavy disruptions with the major highway connecting the two states closed in both directions.
Police said the road was likely to remain shut for some time.
BARRIER HIGHWAY, OLARY— SA Infrastructure & Transport (@DFIT_SA) The Barrier Highway is closed in both directions near Olary due to a serious collision.Please avoid the area.Get live traffic info: https://t.co/TEOjjY7WMR pic.twitter.com/FdueK4mZKQDecember 31, 2023
Motorists coming from NSW will not be able to travel past Broken Hill on the Barrier Highway into SA.
Motorists travelling east will not be able to travel past the Petersburg Road - Peterborough turn-off, about 220km from the border.
NSW authorities said if people needed to travel they could take the Silver City and the Sturt highways instead but that would add at least two hours to the journey.
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