The Herald has learned that police requested assistance from the Fire Service after an "incident" on Ngaio St.
Firefighters have evacuated four homes in the area immediately adjacent to the affected property.
A Fire Service Hazardous Materials Unit is also at the scene.
Police are expected to release more information soon, as the lead responder to the incident.
The cylinder is currently being removed and it is understood it will be taken away for investigation.
The incident occurred at a Housing New Zealand property. Police referred inquiries to the agency, saying it was best placed to disseminate information about the incident.