Last week's fire at Eastown Timber left dust and debris on surrounding areas in Whanganui East, prompting one resident to give a sample to Horizons Regional Council for testing.
Bridget McArthur said her main worry was that some of it contained asbestos.
"The morning of the fire I could feel something dropping on my arm and at first I thought it was spitting.
"Then I realised it was probably fall-out. My car ended up covered in ash."
McArthur said some of the debris was red, fibrous material between 2cm and 12cm long.
She collected pieces from around the intersection of Jellicoe and Maketu streets, which is a few hundred metres from Eastown Timber on Holyoake St.
"It's concerning because we don't know what it is. I've got animals who can cart this stuff in on their bodies.
"No one else seems to have queried it, which is just bizarre."
A Horizons compliance monitoring spokesperson said the samples had been collected and delivered to Public Health at the Whanganui Hospital, who offer a free asbestos testing service
"Any steps from there will depend on the test results.
"If the result is positive a response would be coordinated between Horizons, Whanganui District Council and likely Public Health."
Fire and Emergency New Zealand risk reduction adviser John Hotter said the roof of one building that caught fire last Friday was made of asbestos.
"There was a lot of airborne ash in the fire, but without seeing the actual material I'm not able to tell exactly what it is," Hotter said.