The accident happened just before 7 a.m. on Saturday.
According to the regional supervisor with N.C. DEQ, Landon Davidson, the tanker crashed in the eastbound lane of I-26, near mile marker 61.
He says crews recovered between 500 and 600 gallons of milk out of a storm water ditch at the crash site, but milk flowed into Cove Creek.
The milk went downstream and is now entering Green River, Davidson says.
He says it will continue to dilute as it moves downstream.
On Saturday morning, Kyle Rhodes and his wife, Cindi, took their dog, Maisy on a hike in the Bradley Falls area. They discovered the milk-filled creek, but at the time they were not sure what was causing the discoloration.
Game wardens are monitoring the spill and the primary concern is to aquatic life.
Davidson says that as the milk degrades, it removes oxygen from the water.
He says decreased oxygen can endanger fish and aquatic insects.
No fish have been killed so far.