High levels of the chemical benzene were registered in the air near Sarnia, Ont., in April, forcing neighbouring Aamjiwnaang First Nation to declare a state of emergency after people became ill with headaches,

Aamjiwnaang First Nation issued the precautionary evacuation notice for select areas near the plant’s fence line in advance of the work underway this week to remove benzene from the INEOS Styrosolution site.

The First Nation says the removal was expected to result in some increased benzene levels until Saturday and monitors were set up around the community to keep tabs on emissions.