Insp. Mac Richards says the woman found the package in the driveway of the rural home on Stuart Avenue, Friday morning.
He say she brought the package inside the house, where it exploded.
Richards says the woman, as well as a man, were treated in hospital but one of the patients has been transferred to Victoria.
Other than plastic shopping bags, the contents of the package and where it came from are still being investigated.
Richards says the RCMP's explosives-disposal unit was called in and is assisting with the investigation.
"I'm not sure what it is," he says. "There's obviously some kind of chemical reaction but, you know, the intent or how or why — that I don't know."
In a release, Port Alberni RCMP asks that anyone who finds a suspicious item, "is urged not to disturb it, and contact police for assistance."
Also On HuffPost: