Senior officer of Te Awamutu Fire Brigade, Lex Soepnel, estimated one to two tonnes of molasses was spilt onto the road.
"We had one appliance and a water tanker turn out and kept the spillage to a minimum until contractors and local authorities arrived on the scene," he said.
The trucking company sent another vehicle and the molasses which remained in the damaged tanker was pumped across to be removed.
Otorohanga District Council executive assistant David Dowd told the Courier Ngahape Road was still closed until after midday on Wednesday.
"We've put turning points in place for heavy vehicles to take a detour," he said.
"It's a really sticky mess on the road and will take a lot of water to disperse it.
"Fortunately molasses is a non-hazardous substance."
Mr Dowd said the driver was not injured but was shaken by the incident.
