The smell of sulphur in the air is caused by Mt Tongariro yet is no cause for concern, authorities say.
A distinctive sulphur odour has been noticed in parts of the North Island during the past few days.
Horizons Regional Council emergency manager Shane Bayley said the council had received a number of calls from people in the Wanganui region.
"The sulphur we're smelling is the result of wind drift from the mountain. It is reminiscent of Rotorua but it is not a cause for concern," Mr Bayley said.
He said the smell had been common since Mt Tongariro erupted on August 6.
"Our air quality monitoring sites in Taumarunui and Taihape are not showing any elevated presence of fine air particles. However, our team will be keeping an eye on the situation and will alert the public if this situation changes," Mr Bayley said.
Since the eruption, seismic activity at Mt Tongariro has remained low but GNS Science is continuing to monitor it.