noun
suspicious object; suspicious substance
Used especially in security contexts for unattended bags, packages, or unknown substances that may pose a threat.
駅で不審物が見つかり、警察が調べている。
A suspicious object was found at the station, and the police are investigating.
不審物を発見したら、すぐに係員に知らせてください。
If you find a suspicious object, please notify a staff member immediately.
危険物 means 'dangerous goods' or 'hazardous materials' in general, whereas 不審物 emphasizes the suspicious nature of an object whose danger is not yet confirmed.
Compound of 不審 (ふしん, 'suspicious, doubtful') and 物 (ぶつ, 'thing, object').