There's a distinct smell of Rotorua in the Horowhenua today.
Mt Tongariro, which erupted last week, is sending whiffs of sulphur into the air and it's heading south.
Residents in the Levin region in particular are reporting the rotten-egg smell.
But Brad Scott from GNS Science says the volcano is de-gassing.
"We've had molten material come into the volcano at depth and that molten material's de-gassing, freeing to the surface and those are the big white plumes that you see in the photographs from the volcano, that's the gas coming off it."
Mr Scott says it's all part of the natural process after an eruption.