A chimney stack at Christchurch hospital is causing concern and some areas are now off-limits until further checks are made.
Canterbury District Health Board says a problem was found with the steel reinforcing inside the stack during a routine inspection.
Staff working in the vicinity were moved out of their offices and workshops on Tuesday.
More tests will be carried out on Wednesday morning.
Until then, the area is cordoned off, along with St Asaph and Antigua streets in the vicinity. Traffic diversions are in place.
The hospital's boilers are continuing to operate.