The cost of dealing with asbestos in two Auckland hospital buildings could exceed $10 million.

Brown asbestos - linked to lung-lining cancer - was found in April on ceiling tiles in roof cavities at the old Auckland Hospital, which will be used for administration and to house some post-birth mothers and their babies.

Asbestos has also been found in the old Green Lane Hospital, which is being refurbished into stage two of the new Greenlane Clinical Centre for day surgery and outpatient clinics.

The general manager of the new Auckland City Hospital, Nigel Murray, said yesterday asbestos had been removed from the two buildings, and from many other New Zealand hospitals, in the 1980s and 1990s.

Large amounts had been taken out, but clearly some had been left. All the dust was being cleaned out so there was no risk of airborne contamination.

"In some areas to get the asbestos out creates more risk. Where it's contained ... the best thing is to isolate it and further contain it by encapsulating it, spraying it with a specialised polymer that bonds it and locks it into an inert state."

He gave an assurance the buildings would be safe. The full cost was not known, but could top $10 million.

Herald Feature: Health system