Thousands of Canterbury homeowners could have been exposed to asbestos without being aware of it, during repairs to their houses after the 2010 and 2011 earthquakes, Radio New Zealand reports.
WorkSafe is investigating the way Fletcher EQR handles any asbestos it finds in houses.
Christchurch medical officer of health Alistair Humphrey said anyone affected would be at risk of developing the cancer mesothelioma.
But Registered Master Builders chief executive Warwick Quinn said asbestos is generally found in areas that are hidden, and he doubts any homeowners would have been exposed to it.
However, Dr Humphrey does not buy that explanation. He said there are plenty of ways people could have been exposed to asbestos without even being aware.
The Earthquake Commission said it is more than satisfied with how Fletcher EQR has handled asbestos.
