Canada's second-largest container shipping terminal is closed and will re-open after the Labour Day holiday following what authorities at the Port of Prince Rupert described as an "incident" Sunday morning.

DP World, the company that owns the container terminal, said the incident took place at 5 a.m. PT. A spokesperson said 11 workers had to get medical treatment at the hospital with symptoms of respiratory and eye irritation. They have all since been released.

Little information was released about what happened.

Port spokesperson Caroline Keddy would not elaborate beyond stating the incident was contained within port land and property.

"There's no spill right now. It's just an incident," she said.

"The workers are okay," said Robert Ashton, president of the International Longshore Workers Union. Ashton said he didn't know the nature of the incident, adding there is an investigation.

DP World said it suspended operations and evacuated the premises until it was able to complete air quality testing on site. It said an external industrial hygienist also conducted on-site assessments and the site was declared safe by 4:30 a.m. Monday.

The terminal will resume operations on Tuesday.

Port of Prince Rupert

The expansion of the Fairview container terminal at the Port of Prince Rupert makes it the second-largest container handling facility in Canada, trailing only Delta, B.C. (Prince Rupert Port Authority)

Second largest container port

The incident happened in the same week as the port celebrated the completion of a two-year project by DP World to expand its Fairview Container Terminal.

The major upgrade expanded the port's handling capacity by more than 50 per cent and made it the second-largest container handling facility in Canada.

The port is known to be a reliable entry point for companies that need their goods to arrive on time, according to Mark Szakonyi, editor of the ocean shipping publication, Journal of Commerce.

He said because the Prince Rupert Port has been consistently reliable, companies have started shipping more goods through the northern port.

With files from Andrew Kurjata