Corporate affairs manager at GrainCorp David Ginns said there had been a dramatic increase in grain coming into GrainCorp sites with massively elevated phosphine levels.

Mr Ginns said GrainCorp could not accept the loads as they posed a serious health and safety risk, as well as posing a threat to export markets.

He said in a three-day period recently, there were eight trucks detected at Newcastle port with phosphine levels more than three times the recommended levels.

He reiterated to growers that if the level of phosphine in a load is above 0.3 parts per million, the load may be classified as 'Goods too Dangerous to be Transported', and both the party loading and the party transporting the grain may be fined or prosecuted.

There will be a zero tolerance policy to grain delivered to a GrainCorp site with a detected phosphine gas level higher than 0.3ppm, the load will not be received and the vehicle will be instructed to leave the site.