One man has since been arrested.Police Scotland said the device was discovered on the ground floor of Glen Tower flats in Motherwell around 1am on Thursday morning.
Residents were evacuated as a precaution while bomb squad officers investigated the suspicious item. The community room of the tower block was designated as a polling station.
Shortly after 11.30am, Chief Inspector Mark Leonard said: “Police in Motherwell have arrested a 48-year-old man in connection with a suspicious device found on the ground floor of Glen Tower flats, Motherwell around 1am on Thursday, 12 December, 2019.
"Enquiries are ongoing."
In a statement this morning North Lanarkshire Council advised the public to use an alternative polling station.
The council said: "Due to a police incident, voters registered to vote at Glen Tower, Motherwell please now attend a polling station at Knowetop Primary School, Knowetop Avenue, Motherwell from 7am.
"All residents are safe and police are carrying out inquiries."