The Nova Chemicals offices in downtown Calgary were evacuated Friday morning due to a suspicious package, a day after the company's plant near Joffre, Alta., was the subject of a threat.

Calgary police shut down Seventh Avenue between Ninth and 10th Streets S.W. for a period of time on Friday as they investigated the suspicious package. C-Train service was also suspended in the area.

Employees returned to the building later in the day, after police deemed everything was safe, the company said in a release Friday afternoon.

The incident comes a day after RCMP said they were investigating a threat directed at the Nova Chemicals plant in central Alberta. They wouldn't say anything about the nature of that threat.

The Nova Chemicals plant near Joffre, Alta., is seen in this photo. (Nova Chemicals)

"The RCMP remain onsite at Nova Chemicals' Joffre site and are assessing if a risk exists," the company said in the Friday-afternoon release.

RCMP said on Thursday they had deployed resources to the plant that "will remain in the area to confirm the property is safe."

The company said it is "cooperating fully with local police and the RCMP to investigate and resolve the situation."

Joffre is about 175 kilometres north of Calgary.