But Mr Peet said he understood that the odour was stronger at other times of the day and Horizons would request a log of odour complaints received by the Wanganui District Council.
Mr Peet said the aerator was shut down before Horizons visited the plant.
He said he was unable to confirm that an industrial site contributed to the smell.
Mr Peet said when Horizons receives complaints to its pollution hotline, these are investigated by duty staff to verify the nature of the complaint.
"The community play a vital role in advising staff of environmental issues," he said.
Meanwhile, Wanganui District Council's infrastructure manager, Mark Hughes, said the partial shutdown of the plant was likely to continue for the rest of the week.
"The aerators, except one small one, remain shut down until the protein compounds can be treated and limited aeration and bioaugmentation recommenced," Mr Hughes said.