Two more schools have been added to Environment Canterbury's (ECan) database of potentially contaminated land.
Sumner Primary School was "completely missed" when consultants and staffers viewed aerial photographs from the 1940s onwards, ECan land contamination team leader Davina McNickel said.
Meanwhile, a computer glitch on April 15 meant Our Lady of Fatima School in Mairehau and four other non-school sites were mysteriously deleted. They are being redesignated as potentially contaminated.
"We were expecting the odd mistake," McNickel said.
The list of schools with potentially contaminated land in Christchurch now stands at 126 out of 146. More than 70 per cent of those affected are suspected of using pesticides on sport turfs to combat weeds, diseases and insects from the 1940s onwards. The chemicals can remain for long periods and many have been banned for years.
Canterbury medical officer of health Dr Ramon Pink said it was "very unlikely" the level of contamination would be high enough to affect health.
ECan advises schools and landowners with potentially contaminated land to let sleeping dogs lie for the time being.
"If you don't have to disturb it, don't," ECan strategic programmes manager Don Chittock said.
On Monday, The Press revealed that 85 per cent of Christchurch schools - primary, secondary, public and private - were on the potentially contaminated list. An analysis of the schools not on the list revealed it was unlikely that Sumner Primary was unaffected. Two other schools in the seaside village, Our Lady Star of the Sea school and the Van Asch Deaf Education Centre, were in the database. Our Lady of Fatima was identified the same way.
- The Press