Shell is investigating odour concerns at the Sarnia Manufacturing Centre in Corunna.
The company said it is aware that any odours from the site can be an issue to neighbours and any concerns raised are being taken seriously.
The company reported a unit trip around 7:30 a.m. on Wednesday.
Shell said it resulted in larger than normal flaring and increased noise.
The company said at the time it could take up to 36 hours for the unit to return to service.