Tap water at some houses had high levels of a chemical called manganese.
Police are at the scene trying to retrieve the vehicle.
It took the victim's co-workers 10 minutes to remove her hand from the machinery.
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Police said the incident did not appear to be gang-related.
Police are making enquiries.
There were fears gang tensions had broken out again in the city after one person was hospitalised.
The man has not sustained any injuries.