WINDSOR, ONT. -- Wheatley remains under a state of emergency one week after it was declared.

Crews are still trying to locate the source of the hydrogen-sulfide gas, which closed four businesses and evacuated 27 residents from their homes.

The gas is flammable and toxic, and while the level of gas has dropped, Chatham-Kent Chief Administrative Officer Don Shropshire says the municipality is reluctant to lift the state of emergency at this time.

Shropshire says it is potentially dangerous to do so without knowing the source of the gas because the concentration of sour gas could rise again.

Shropshire says it is possible it is coming from either an abandon gas well or a forgotten water well.

Without knowing the source, the province cannot provide much help according to Shropshire as the Ministry of Natural Resources would help deal with the situation if the source was a gas well, but it is the Ministry of the Environment, which would help if it was coming from a water well.

He adds the municipality has hired a private firm with experience if this field to help develop a plan to locate the source.