Hamilton police are searching for a portable x-ray machine investigators believe was stolen from the site of a fatal fire investigation in the lower city.

Officials from the Ontario Fire Marshal's office were sifting through the rubble at 70 Niagara Street, where a fire killed a mother and her two children after it tore through the home that Saturday evening.

When doing inventory of equipment used there days later, fire marshal investigators realized that a piece of equipment was stolen from their truck while at the scene, police say.

"A black pelican brand plastic case containing a portable X-Ray machine is missing and presumed stolen," Hamilton police said in a news release.

"While this piece of investigative equipment poses no risk when handled, if the equipment were to be powered up, the radiation emitted can be harmful to humans."

Police are warning the public about this risk and are asking anyone with information about the device to contact police or Crime Stoppers.