The Waikato Regional Council says it's unlikely a truck that crashed into the Awakino River spilling whey will significantly damage the environment.
The truck crashed into the southern Waikato river on Sunday morning and overturned.
The regional council says initial reports suggested diesel and whey were leaking from the truck into the river.
Council spokesperson Rob Dragten says up to 2000 litres of whey spilt into the river, which is a relatively small amount.
The council expects any whey that got into the river to be diluted reasonably easily and not to cause ongoing problems.
Mr Dragten says the truck's diesel tanks weren't punctured so no diesel leaked into the river.
The truck's driver was unharmed in the crash.