Bromley School in eastern Christchurch is closed today because of a bad smell.
A notice on the primary school's website said a strong gas-like odour was first noticed yesterday morning and the Fire Service was called.
Firefighters and ambulance failed to locate the source of the smell and the school was given the all-clear about 10.15am.
Children stayed inside as a precaution but the smell returned stronger in particular areas in the afternoon.
The odour remained today, however, and a message on the school's answerphone said it would remain closed until the source of the smell was identified.
Principal Scot Kinley put out a notice that he had decided to close the school until there was a clear answer on what the smell was and its source.
The Canterbury regional council said it was trying to locate the source of the smell.
The council said the Fire Service identified two piles of earth at a site in Maces Road which could be the source.
It said it was too early to confirm the source, but officers were investigating.