It is understood the 9.30am freight train from Ballina to North Wall in Dublin hit a tractor at a level crossing in Co Roscommon.
The fatal rail crash was at Ballymacfrane near the village of Donamon in Co Roscommon.
The driver of the tractor was killed.
The line is closed until further notice and a bus service is available for passengers between Roscommon and Westport.
Rail accident investigators have just arrived at the scene which is still sealed off by gardaí.
