The incident happened about 1.40pm on Sunday afternoon at the train crossing on Given Rd, which sits off State Highway 1 between Gore and Mataura.
Emergency services attended the scene with two people requiring medical attention. One was transported to Kew Hospital in a serious condition.
The other was assessed at the scene and did not require hospitalisation.
A police spokesperson stated the investigations were still under way, with no more information to share at the time of reporting.
Kiwirail Acting Chief Operations Officer Paul Ashton said, in a statement, the level crossing was not on a public road and was protected by signage.
The train crew was uninjured and the train received minimal damage. However services were delayed by three hours as a result of the accident.
Mr Ashton said there were measures train operators could deploy to avoid a collision such as blowing their horn and deploying emergency brakes, but "there is often little else they can do to stop the train in a hurry".
Mr Ashton stated it was important to be proactive when it comes to safety on level crossings, with Kiwirail also taking this issue seriously.
"Trains can appear at any time whether they are expected or not. Trains always have right of way and travel faster than they appear to.
"KiwiRail regards safety as paramount and strongly encourages road users to follow the signage at level crossings."
