Shell was dealing with a sheen Tuesday morning on the St. Clair River.
The company said the light sheen was first noticed on Talfourd Creek following heavy rain.
Shell said it took measures to contain and remove the sheen and said the situation is being closely monitored.
The company issued an all clear at around 6:20 p.m.
An all clear had been issued at around 1:20 p.m. in error.