Environment Canterbury has finished its investigation into the source of a stench which clung to eastern Christchurch last week.

The smell - described as a strong gas odour - caused problems and complaints, with Bromley School forced to close for two days because of the odour.

ECAN officers have narrowed down the pong to near the Bromley Waste Water Treatment Plant.

The investigation is now closed but ECAN will continue to monitor the situation.

Christchurch residents were disgusted by the strange smells.

A number of callers told Newstalk ZB's Chris Lynch the smell didn't go away quickly, and were concerned it might be dangerous.

"It's that type of gas it get's in the back of your throat as well I have rung ECan and the council they just said that it's not toxic. Well I said, how would you know if it was toxic or not," one caller said.

Another called in and said: "That smell yesterday was very very strong and it reminded me of a ruptured gas main. It sort of scared me a wee bit because it was so intense."