ECan is still unsure of where a strange smell is coming from in Christchurch that has kept students of a primary school at home for another day.
Bromley School, in the east of the city, closed Wednesday afternoon as a precaution after gas was smelled in "pockets" of the school grounds, said principal Scot Kinley.
"We were given the all clear by emergency services at 10:15am. The children stayed inside as a precaution until 12:50pm," he wrote on the school's Facebook page.
"The gas smell returned in pockets around 1:30pm and become stronger in certain areas after 2pm."
The school's staff have had a meeting this morning and are on site, but have been told if they feel uncomfortable or unwell they can go home.
The fire service has received eight calls about the smell in the past 24 hours. It is working with Christchurch City Council and Environment Canterbury (ECan) to locate the source.
ECan deployed incident response officers in the Bromley area, who are using odour software to help identify the source.
"The fire service also contacted us after identifying piles of earth at a site in Maces Road as the potential source of the smell," said ECan regional leader investigations and incidents Valyn Barrett.
Officers in the area last night said the smell was noticeable but not offensive.
"However, we understand from complainants that it was extreme at the time of their complaints," said Ms Barrett.
Officers at the suspected site before 8am Thursday morning and found no offensive odour.
"Since then we have received subsequent complaints from surrounding areas, including Wainoni, Dallington and Bexley," Mr Barrett said.
"An officer is visiting all the complainants."
ECAn has had a total of 12 calls today about the odour and Mr Barrett says while they have a rough idea of where it's coming from, it's unlikely they will find the actual source.
"With the odours it's difficult because they're carried by the wind," he says.
"We've spoken to the health department and as far as I'm aware they're not concerned about it."
ECan gets 6000 calls a year about strange or bad smells.
"It's nothing new for us," Mr Barrett says.
At Living Earth Limited, a subsidiary of Waste Management in Bromley, odour testing done in the past 48 hours shows everything is in order with normal operations. It also showed the wind direction was not in the direction of the Bromley School.
General manager technical services for Living Earth, David Perkins, is confident Living Earth is not the source of the odour that has impacted the school.